What are ALT and AST liver function tests. How to interpret normal, high, and low levels. What factors can affect liver enzyme test results. When should you be concerned about abnormal liver function test results. How are liver function tests used to diagnose and monitor liver conditions.

Understanding Liver Function Tests: ALT and AST Explained

Liver function tests (LFTs) are blood tests that provide valuable insights into the health and functionality of the liver. Among these tests, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are two key enzymes that play a crucial role in assessing liver health. These enzymes, when found in elevated levels in the bloodstream, can indicate liver cell damage or disease.

ALT, formerly known as serum glutamate-pyruvate transaminase (SGPT), is primarily found in the liver. AST, previously called serum glutamic-oxaloacetic transaminase (SGOT), is present in various tissues, including the liver, heart, and muscles. While both enzymes are important markers of liver health, ALT is considered more specific to liver damage due to its predominant presence in liver cells.

What do ALT and AST levels indicate?

Elevated levels of ALT and AST in the blood can suggest liver cell damage or inflammation. However, it’s important to note that these enzymes can also be elevated due to conditions unrelated to liver disease. For instance, muscle injury or certain medications can cause a temporary increase in these enzyme levels.

Normal, High, and Low Levels: Interpreting ALT and AST Results

Understanding the normal ranges for ALT and AST is crucial for interpreting liver function test results. However, it’s important to remember that these ranges can vary slightly depending on the laboratory and the specific testing methods used.

What are considered normal ALT and AST levels?

Generally, normal ALT levels range from 7 to 55 units per liter (U/L) for males and 7 to 45 U/L for females. For AST, the normal range is typically between 8 and 48 U/L for males and 6 to 40 U/L for females. It’s worth noting that these ranges can differ based on factors such as age, gender, and ethnicity.

When are ALT and AST levels considered high?

ALT and AST levels are typically considered elevated when they exceed the upper limit of the normal range. Mild elevations (less than 1.5 times the upper limit of normal) may not always indicate significant liver disease. However, levels more than 10 times the upper limit of normal often suggest severe liver damage, such as that caused by viral hepatitis or drug-induced liver injury.

Can ALT and AST levels be too low?

While much attention is given to elevated liver enzyme levels, low levels of ALT and AST are generally not a cause for concern. In fact, very low levels of these enzymes are rarely seen and are not typically associated with liver disease. However, in some cases, extremely low levels might indicate malnutrition or vitamin B6 deficiency.

Factors Affecting ALT and AST Levels

Several factors can influence ALT and AST levels, which is why interpreting these test results requires consideration of the patient’s overall health status and other clinical factors.

• Gender: Males typically have slightly higher normal ranges for both ALT and AST compared to females.
• Ethnicity: Some studies suggest that normal ranges may vary among different ethnic groups.
• Body Mass Index (BMI): Obese individuals often have mildly elevated liver enzyme levels.
• Alcohol consumption: Regular alcohol intake can lead to elevated liver enzymes, particularly AST.
• Medications: Certain drugs can affect liver enzyme levels, either by causing liver damage or through other mechanisms.
• Exercise: Intense physical activity can temporarily elevate AST levels due to muscle breakdown.

Common Pitfalls in Interpreting Liver Function Tests

Interpreting liver function tests can be challenging, and there are several pitfalls that healthcare providers should be aware of to ensure accurate diagnosis and appropriate patient management.

Are normal ALT and AST levels always indicative of a healthy liver?

No, normal ALT and AST levels do not always guarantee a healthy liver. Patients with chronic hepatitis or cirrhosis can sometimes have normal liver enzyme levels. This is why it’s crucial to consider other clinical factors and additional tests when assessing liver health.

Can conditions other than liver disease cause elevated ALT and AST?

Yes, several conditions unrelated to liver disease can cause elevated ALT and AST levels. These include muscle injury, myopathy, and certain medications. In some cases, what appears to be liver disease based on elevated enzymes might actually be another condition altogether.

For example, severe alcoholic hepatitis can sometimes be confused with cholecystitis or cholangitis due to similar laboratory values and symptoms. Conversely, patients who have recently passed common bile duct stones might be misdiagnosed with acute hepatitis because ALT and AST levels can rise immediately, while other markers like alkaline phosphatase and γ-glutamyltransferase take several days to become elevated.

Assessing Overall Liver Function

While ALT and AST are important markers of liver cell damage, they don’t provide a complete picture of liver function. To assess overall hepatic function, healthcare providers often use additional tests and scoring systems.

What other tests are used to evaluate liver function?

In addition to ALT and AST, other important tests for assessing liver function include:

• Albumin: A protein produced by the liver that can indicate the liver’s synthetic function.
• Bilirubin: A breakdown product of red blood cells that can be elevated in various liver diseases.
• Prothrombin Time (PT): A measure of blood clotting that can be affected by liver disease.
• Alkaline Phosphatase (AP): An enzyme that can be elevated in liver diseases, particularly those affecting the bile ducts.
• γ-Glutamyltransferase (GGT): An enzyme that can be elevated in liver disease and is particularly sensitive to alcohol use.

How is overall liver function assessed?

One common method for assessing overall liver function is the modified Child-Turcotte grading system, which incorporates albumin, bilirubin, and prothrombin time values. This system helps classify the severity of liver disease and can be useful in predicting outcomes and guiding treatment decisions.

Special Considerations in Liver Function Testing

Certain scenarios require special consideration when interpreting liver function tests to avoid misdiagnosis and ensure appropriate patient care.

How should isolated enzyme elevations be interpreted?

Isolated elevations of certain liver enzymes can sometimes be misleading:

• Isolated GGT elevation: This may be induced by alcohol consumption or certain medications, often without actual liver disease.
• Isolated AP elevation: In an asymptomatic patient with normal GGT, this could indicate bone growth or injury, or conditions like primary biliary cirrhosis. AP levels also naturally rise in late pregnancy.
• Isolated unconjugated bilirubin elevation: This might suggest Gilbert syndrome or hemolysis rather than liver disease.

What about ammonia levels in liver function assessment?

Blood ammonia levels are sometimes used in liver function assessment, particularly in cases of suspected hepatic encephalopathy. However, it’s important to note that ammonia levels are not necessarily elevated in all patients with hepatic encephalopathy. The determination of blood ammonia levels is most useful in patients with altered mental status of new onset or unknown origin.

Liver Function Tests in Chronic Liver Diseases

In chronic liver diseases such as hepatitis C and cirrhosis, the relationship between liver enzyme levels and disease severity can be complex.

How do liver enzyme levels correlate with disease severity in chronic hepatitis?

In chronic hepatitis C, for example, serum ALT levels correlate only moderately well with liver inflammation. This is partly because in chronic liver diseases, liver cell death occurs not only by necrosis (which releases large amounts of enzymes) but also by apoptosis (programmed cell death). Hepatocytes dying by apoptosis presumably synthesize less AST and ALT as they wither away, which may explain why at least one-third of patients infected with hepatitis C have persistently normal ALT levels despite ongoing liver damage.

What does this mean for patient management?

This complexity in chronic liver diseases underscores the importance of not relying solely on ALT and AST levels for disease monitoring. Regular liver biopsies, imaging studies, and other non-invasive markers of liver fibrosis may be necessary to accurately assess disease progression and guide treatment decisions in patients with chronic liver conditions.

The Future of Liver Function Testing

As our understanding of liver diseases evolves, so too does the field of liver function testing. Researchers are continually working to develop new, more accurate markers of liver health and disease progression.

What new liver function tests are being developed?

Several promising new biomarkers and testing methods are being investigated:

• Cytokeratin-18 fragments: These may provide a more direct measure of liver cell death by apoptosis.
• MicroRNAs: Certain circulating microRNAs are being studied as potential biomarkers of liver injury and disease progression.
• Metabolomics: This approach involves analyzing the metabolic profile of patients to identify patterns associated with liver disease.
• Advanced imaging techniques: Methods like elastography are being refined to non-invasively assess liver fibrosis and cirrhosis.

While these new approaches show promise, traditional liver function tests like ALT and AST remain crucial tools in the diagnosis and management of liver diseases. As research progresses, it’s likely that a combination of traditional and novel biomarkers will provide the most comprehensive assessment of liver health.

In conclusion, understanding and correctly interpreting liver function tests, particularly ALT and AST levels, is crucial for effective diagnosis and management of liver diseases. While these tests provide valuable information, they must always be considered in the context of the patient’s overall clinical picture, including symptoms, risk factors, and other laboratory and imaging findings. As our knowledge of liver pathophysiology continues to grow, so too will our ability to accurately assess and monitor liver health through blood tests and other diagnostic tools.

Special Considerations in Interpreting Liver Function Tests

DAVID E. JOHNSTON, M.D.

A number of pitfalls can be encountered in the interpretation of common blood liver function tests. These tests can be normal in patients with chronic hepatitis or cirrhosis. The normal range for aminotransferase levels is slightly higher in males, nonwhites and obese persons. Severe alcoholic hepatitis is sometimes confused with cholecystitis or cholangitis. Conversely, patients who present soon after passing common bile duct stones can be misdiagnosed with acute hepatitis because aminotransferase levels often rise immediately, but alkaline phosphatase and γ-glutamyltransferase levels do not become elevated for several days. Asymptomatic patients with isolated, mild elevation of either the unconjugated bilirubin or the γ-glutamyltransferase value usually do not have liver disease and generally do not require extensive evaluation. Overall hepatic function can be assessed by applying the values for albumin, bilirubin and prothrombin time in the modified Child-Turcotte grading system.

The commonly used liver function tests (LFTs) primarily assess liver injury rather than hepatic function. Indeed, these blood tests may reflect problems arising outside the liver, such as hemolysis (elevated bilirubin level) or bone disease (elevated alkaline phosphatase [AP] level).

Abnormal LFTs often, but not always, indicate that something is wrong with the liver, and they can provide clues to the nature of the problem. However, normal LFTs do not always mean that the liver is normal. Patients with cirrhosis and bleeding esophageal varices can have normal LFTs. Of the routine LFTs, only serum albumin, bilirubin and prothrombin time (PT) provide useful information on how well the liver is functioning.

The general subject of LFTs^1,2 and the differential diagnosis of abnormal LFTs in asymptomatic patients^3–5 have been well reviewed. This article discusses some common pitfalls in the interpretation of LFTs. Hints for interpreting these tests are presented in Table 1.

Situation	Comments
Mildly elevated ALT level (less than 1.5 times normal)	ALT value could be normal for gender, ethnicity or body mass index.
	Consider muscle injury or myopathy.
Alcoholic hepatitis	Laboratory values can appear cholestatic, and symptoms can mimic cholecystitis.
	Minimal elevations of AST and ALT often occur.
AST level greater than 500 U per L	The AST elevation is unlikely to result from alcohol intake alone.
	In a heavy drinker, consider acetaminophen toxicity.
Common bile duct stone	Condition can simulate acute hepatitis
	AST and ALT become elevated immediately, but elevation of AP and GGT is delayed.
Isolated elevation of GGT level	This situation may be induced by alcohol and aromatic medications, usually with no actual liver disease.
Isolated elevation of AP level (asymptomatic patient with normal GGT level)	Consider bone growth or injury, or primary biliary cirrhosis.
	AP level rises in late pregnancy.
Isolated elevation of unconjugated bilirubin level	Consider Gilbert syndrome or hemolysis.
Low albumin level	Low albumin is most often caused by acute or chronic inflammation, urinary loss, severe malnutrition or liver disease; it is sometimes caused by gastrointestinal loss (e. g., colitis or some uncommon small bowel disease).
	Normal values are lower in pregnancy.
Blood ammonia level	Blood ammonia values are not necessarily elevated in patients with hepatic encephalopathy.
	Determination of blood ammonia levels is most useful in patients with altered mental status of new onset or unknown origin.

Markers of Hepatocellular Injury

The most commonly used markers of hepatocyte injury are aspartate aminotransferase (AST, formerly serum glutamic-oxaloacetic transaminase [SGOT]) and alanine aminotransferase (ALT, formerly serum glutamate-pyruvate transaminase [SGPT]). While ALT is cytosolic, AST has both cytosolic and mitochondrial forms.

Hepatocyte necrosis in acute hepatitis, toxic injury or ischemic injury results in the leakage of enzymes into the circulation. However, in chronic liver diseases such as hepatitis C and cirrhosis, the serum ALT level correlates only moderately well with liver inflammation. In hepatitis C, liver cell death occurs by apoptosis (programmed cell death) as well as by necrosis. Hepatocytes dying by apoptosis presumably synthesize less AST and ALT as they wither away. This probably explains why at least one third of patients infected with hepatitis C virus have persistently normal serum ALT levels despite the presence of inflammation on liver biopsy.^6,7 Patients with cirrhosis often have normal or only slightly elevated serum AST and ALT levels. Thus, AST and ALT lack some sensitivity in detecting chronic liver injury. Of course, AST and ALT levels tend to be higher in cirrhotic patients with continuing inflammation or necrosis than in those without continuing liver injury.

As markers of hepatocellular injury, AST and ALT also lack some specificity because they are found in skeletal muscle. Levels of these aminotransferases can rise to several times normal after severe muscular exertion or other muscle injury, as in polymyositis,⁸ or in the presence of hypothyroidism, which can cause mild muscle injury and the release of aminotransferases. In fact, AST and ALT were once used in the diagnosis of myocardial infarction.

Slight AST or ALT elevations (within 1.5 times the upper limits of normal) do not necessarily indicate liver disease. Part of this ambiguity has to do with the fact that unlike the values in many other biochemical tests, serum AST and ALT levels do not follow a normal bell-shaped distribution in the population.⁹ Instead, AST and ALT values have a skewed distribution characterized by a long “tail” at the high end of the scale (Figure 1).⁵ For example, the mean values for ALT are very similar from one population to another, but the degree to which the distribution is skewed varies by gender and ethnicity. The ALT distributions in males and nonwhites (i.e., blacks and Hispanics) tend to have a larger tail at the high end, so that more values fall above the upper limits of normal set for the average population.^10,11

AST and ALT values are higher in obese patients, probably because these persons commonly have fatty livers. ¹² ALT levels have been noted to decline with weight loss.¹³ Depending on the physician’s point of view, the upper limits of normal for AST and ALT levels could be set higher for more obese persons.

Rare individuals have chronically elevated AST levels because of a defect in clearance of the enzyme from the circulation.¹⁴ For both AST and ALT, the average values and upper limits of normal in patients undergoing renal dialysis are about one half of those found in the general population.¹⁵ Mild elevations of ALT or AST in asymptomatic patients can be evaluated efficiently by considering alcohol abuse, hepatitis B, hepatitis C and several other possible diagnoses (Table 2).⁵

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Various liver diseases are associated with typical ranges of AST and ALT levels (Figure 2). ALT levels often rise to several thousand units per liter in patients with acute viral hepatitis. The highest ALT levels—often more than 10,000 U per L—are usually found in patients with acute toxic injury subsequent to, for example, acetaminophen overdose or acute ischemic insult to the liver. AST and ALT levels usually fall rapidly after an acute insult.

Lactate dehydrogenase (LDH) is less specific than AST and ALT as a marker of hepatocyte injury. However, it is worth noting that LDH is disproportionately elevated after an ischemic liver injury.¹⁶

It is especially important to remember that in patients with acute alcoholic hepatitis, the serum AST level is almost never greater than 500 U per L and the serum ALT value is almost never greater than 300 U per L. The reasons for these limits on AST and ALT elevations are not well understood. In typical viral or toxic liver injury, the serum ALT level rises more than the AST value, reflecting the relative amounts of these enzymes in hepatocytes. However, in alcoholic hepatitis, the ratio of AST to ALT is greater than 1 in 90 percent of patients and is usually greater than 2.¹⁷ The higher the AST-to-ALT ratio, the greater the likelihood that alcohol is contributing to the abnormal LFTs. In the absence of alcohol intake, an increased AST-to-ALT ratio is often found in patients with cirrhosis.

The elevated AST-to-ALT ratio in alcoholic liver disease results in part from the depletion of vitamin B₆ (pyridoxine) in chronic alcoholics.¹⁸ ALT and AST both use pyridoxine as a coenzyme, but the synthesis of ALT is more strongly inhibited by pyridoxine deficiency than is the synthesis of AST. Alcohol also causes mitochondrial injury, which releases the mitochondrial isoenzyme of AST.

Patients with alcoholic hepatitis can present with jaundice, abdominal pain, fever and a minimally elevated AST value, thereby leading to a misdiagnosis of cholecystitis. This is a potentially fatal mistake given the high surgical mortality rate in patients with alcoholic hepatitis. ¹⁹

Markers of Cholestasis

Cholestasis (lack of bile flow) results from the blockage of bile ducts or from a disease that impairs bile formation in the liver itself. AP and γ-glutamyltransferase (GGT) levels typically rise to several times the normal level after several days of bile duct obstruction or intrahepatic cholestasis. The highest liver AP elevations—often greater than 1,000 U per L, or more than six times the normal value—are found in diffuse infiltrative diseases of the liver such as infiltrating tumors and fungal infections.

Diagnostic confusion can occur when a patient presents within a few hours after acute bile duct obstruction from a gallstone. In this situation, AST and ALT levels often reach 500 U per L or more in the first hours and then decline, whereas AP and GGT levels can take several days to rise.

Both AP and GGT levels are elevated in about 90 percent of patients with cholestasis.²⁰ The elevation of GGT alone, with no other LFT abnormalities, often results from enzyme induction by alcohol or aromatic medications in the absence of liver disease. The GGT level is often elevated in persons who take three or more alcoholic drinks (45 g of ethanol or more) per day.²¹ Thus, GGT is a useful marker for immoderate alcohol intake. Phenobarbital, phenytoin (Dilantin) and other aromatic drugs typically cause GGT elevations of about twice normal. A mildly elevated GGT level is a typical finding in patients taking anticonvulsants and by itself does not necessarily indicate liver disease.^22,23

Serum AP originates mostly from liver and bone, which produce slightly different forms of the enzyme. The serum AP level rises during the third trimester of pregnancy because of a form of the enzyme produced in the placenta. When serum AP originates from bone, clues to bone disease are often present, such as recent fracture, bone pain or Paget’s disease of the bone (often found in the elderly). Like the GGT value, the AP level can become mildly elevated in patients who are taking phenytoin.^22,23

If the origin of an elevated serum AP level is in doubt, the isoenzymes of AP can be separated by electrophoresis. However, this process is expensive and usually unnecessary because an elevated liver AP value is usually accompanied by an elevated GGT level, an elevated 5′-nucleotidase level and other LFT abnormalities.

In one study,²⁴ isolated AP elevations were evaluated in an unselected group of patients at a Veterans Affairs hospital. Most mild AP elevations (less than 1.5 times normal) resolved within six months, and almost all greater elevations had an evident cause that was found on routine clinical evaluation.

Persistently elevated liver AP values in asymptomatic patients, especially women, can be caused by primary biliary cirrhosis, which is a chronic inflammatory disorder of the small bile ducts. Serum antimitochondrial antibody is positive in almost all of these patients.

Indicators of How Well the Liver Functions

BILIRUBIN

Bilirubin results from the enzymatic breakdown of heme. Unconjugated bilirubin is conjugated with glucuronic acid in hepatocytes to increase its water solubility and is then rapidly transported into bile. The serum conjugated bilirubin level does not become elevated until the liver has lost at least one half of its excretory capacity. Thus, a patient could have obstruction of either the left or right hepatic duct without a rise in the bilirubin level.

Because the secretion of conjugated bilirubin into bile is very rapid in comparison with the conjugation step, healthy persons have almost no detectable conjugated bilirubin in their blood. Liver disease mainly impairs the secretion of conjugated bilirubin into bile. As a result, conjugated bilirubin is rapidly filtered into the urine, where it can be detected by a dipstick test. The finding of bilirubin in urine is a particularly sensitive indicator of the presence of an increased serum conjugated bilirubin level.

In many healthy persons, the serum unconjugated bilirubin is mildly elevated to a concentration of 2 to 3 mg per dL (34 to 51 μmol per L) or slightly higher, especially after a 24-hour fast. If this is the only LFT abnormality and the conjugated bilirubin level and complete blood count are normal, the diagnosis is usually assumed to be Gilbert syndrome, and no further evaluation is required. Gilbert syndrome was recently shown to be related to a variety of partial defects in uridine diphosphate-glucuronosyl transferase, the enzyme that conjugates bilirubin.²⁵

Mild hemolysis, such as that caused by hereditary spherocytosis and other disorders, can also result in elevated unconjugated bilirubin values, but hemolysis is not usually present if the hematocrit and blood smear are normal. The presence of hemolysis can be confirmed by testing other markers, such as haptoglobin, or by measuring the reticulocyte count.

Severe defects in bilirubin transport and conjugation can lead to markedly elevated unconjugated bilirubin levels, which can cause serious neurologic damage (kernicterus) in infants. However, no serious form of liver disease in adults causes elevation of unconjugated bilirubin levels in the blood without also causing elevation of conjugated bilirubin values.

When a patient has prolonged, severe biliary obstruction followed by the restoration of bile flow, the serum bilirubin level often declines rapidly for several days and then slowly returns to normal over a period of weeks. The slow phase of bilirubin clearance results from the presence of delta-bilirubin, a form of bilirubin chemically attached to serum albumin.²⁶ Because albumin has a half-life of three weeks, delta-bilirubin clears much more slowly than bilirubin-glucuronide. Clinical laboratories can measure delta-bilirubin concentrations, but such measurements are usually unnecessary if the physician is aware of the delta-bilirubin phenomenon.

ALBUMIN

Although the serum albumin level can serve as an index of liver synthetic capacity, several factors make albumin concentrations difficult to interpret.²⁷ The liver can synthesize albumin at twice the healthy basal rate and thus partially compensate for decreased synthetic capacity or increased albumin losses. Albumin has a plasma half-life of three weeks; therefore, serum albumin concentrations change slowly in response to alterations in synthesis. Furthermore, because two thirds of the amount of body albumin is located in the extravascular, extracellular space, changes in distribution can alter the serum concentration.

In practice, patients with low serum albumin concentrations and no other LFT abnormalities are likely to have a nonhepatic cause for low albumin, such as proteinuria or an acute or chronic inflammatory state. Albumin synthesis is immediately and severely depressed in inflammatory states such as burns, trauma and sepsis, and it is commonly depressed in patients with active rheumatic disorders or severe end-stage malnutrition. In addition, normal albumin values are lower in pregnancy.

PROTHROMBIN TIME

The liver synthesizes blood clotting factors II, V, VII, IX and X. The prothrombin time (PT) does not become abnormal until more than 80 percent of liver synthetic capacity is lost. This makes PT a relatively insensitive marker of liver dysfunction. However, abnormal PT prolongation may be a sign of serious liver dysfunction. Because factor VII has a short half-life of only about six hours, it is sensitive to rapid changes in liver synthetic function. Thus, PT is very useful for following liver function in patients with acute liver failure.

An elevated PT can result from a vitamin K deficiency. This deficiency usually occurs in patients with chronic cholestasis or fat malabsorption from disease of the pancreas or small bowel. A trial of vitamin K injections (e.g., 5 mg per day administered subcutaneously for three days) is the most practical way to exclude vitamin K deficiency in such patients. The PT should improve within a few days.

BLOOD AMMONIA

Measurement of the blood ammonia concentration is not always useful in patients with known or suspected hepatic encephalopathy. Ammonia contributes to hepatic encephalopathy; however, ammonia concentrations are much higher in the brain than in the blood and therefore do not correlate well.²⁸ Furthermore, ammonia is not the only waste product responsible for encephalopathy. Thus, blood ammonia concentrations show only a mediocre correlation with the level of mental status in patients with liver disease. It is not unusual for the blood ammonia concentration to be normal in a patient who is in a coma from hepatic encephalopathy.

Blood ammonia levels are best measured in arterial blood because venous concentrations can be elevated as a result of muscle metabolism of amino acids. Blood ammonia concentrations are most useful in evaluating patients with stupor or coma of unknown origin. It is not necessary to evaluate blood ammonia levels routinely in patients with known chronic liver disease who are responding to therapy as expected.

Grading Liver Function by Child-Turcotte Class

In communicating among themselves, many physicians use the Child-Turcotte class as modified by Pugh, often termed the “Child class,” to convey information about overall liver function and prognosis (Table 3).²⁹ This grading system can be used to predict overall life expectancy and surgical mortality in patients with cirrhosis and other liver diseases.³⁰

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For elective general abdominal surgery, perioperative mortality is in the neighborhood of several percent for patients who fall into the Child class A, 10 to 20 percent for those in class B and approximately 50 percent for those in class C.³¹ These percentages must be balanced by prognostic considerations when transplantation becomes an option. The presence of cirrhosis by itself is not an indication for liver transplantation, and transplantation is rarely performed in patients who fall into Child class A. For example, the 10-year survival rate is as high as 80 percent in patients with hepatitis C and cirrhosis who have Child class A liver function and no variceal bleeding.³² However, once patients with any type of liver disease fall into the Child-Turcotte class B or class C category, survival is significantly reduced and transplantation should be considered.

Liver Function Blood Tests Explained

Liver Blood Tests Explained

Blood tests and Investigations for Liver Function              

Some of the standard or routine blood tests that your doctor will order to check “liver function” are in reality only able to detect liver damage. These tests may not be sensitive enough to accurately reflect whether your liver is functioning at its optimum level. These tests will usually be abnormal in significant liver disease or liver distress; however, they can still give normal readings in some cases of mild liver disease.  

Healthy ranges for Blood tests for Liver Function

ALT 0 – 45 U/L

GGT 0 – 45 U/L

AST 0 – 45 U/L

ALP 30 – 120 U/L

BILIRUBIN 0 – 20 U/L or 0.174 to 1.04 mg/dL

ALBUMIN 38 – 55 g/L or 3.8 to 5.5g/dL 

AFP 20 – 32 g/L or 2 to 3.2g/dL

ALT
(alanine aminotransferase), sometimes called SPGT just to confuse us,  is elevated showing inflammation of the liver.

Our ALT shows up high whenever our liver is dealing with any infection or poison or even a hard to digest food such as fried meat. It is common for them to be high in people who have recently had alcohol or paracetamol. With infections, and these can be other diseases like flu or an septic wound they go up as the liver fights back. If they are constantly in the 50 to 200 range we term the hepatitis B infection active. ALT’s range from 0 up to 3000 or so in many acute hepatitis cases. They change with every meal so it is important not to panic if they go from 20 to 45 after a few months. All scores below 45 indicate a perfectly healthy score.

GGT
(gamma glutamyl transpeptidase) is elevated in those who use alcohol or toxins.

Our GST shows up high between 50 and 200 if we are often taking paracetamol or using alcohol a lot. It is often a sign of alcoholism or longer term liver damage, but can be reversed by adopting a alcohol free or toxin free lifestyle.

BILIRUBIN 

If our Bilirubin is elevated, the patient may have a yellow colour skin and eyes, jaundice. Bilirubin is a bile product made by the liver to digest food and it often is overproduced when we first get Hepatitis B or C, then it back fires into the blood stream causing the yellow effect to eyes and skin. It can cause itching and skin irritation as it is sweated out. If it goes up during chronic Hepatitis B or C infection it is a sign of poor food and drink or liver disease. Milk thistle herbal pills are proven to help lower Bilirubin scores so many Hepatitis patients take it.

AFP
(Alpha Feta Globulin Protein). If our AFP is elevated it usually mean excessive inflammation in the liver and/or immune system. Very high levels may be seen in some types of cancers. It is important the many women diagnosed during pregnancy remember it goes up sometimes because of Pregnancy, a score of 40 g/l is not a sign of liver cancer, scores that may indicate a cancer tend to be in the hundreds

AST
(aspartate aminotransferase) also called SGOT, is elevated in heart, muscle and liver diseases.

ALP
(alkaline phosphatase) is elevated in many types of liver and non liver disease.

ALBUMIN
falling levels of blood albumin show deteriorating liver function.

Up to 80% of Hepatitis B and C patients usually have normal, perfectly healthy scores for liver function, these are termed inactive or healthy patients.

Viral Hepatitis Liver Tests – the 4 main Results and Stages

Viral Hepatitis Patients tend to present with 4 types of LFT Result, 3 factors most affect the liver results 

Viral Load, Time Infected and Toxins

Stage 1 – All Normal 

Means hepatitis is having little effect and you are best monitored yearly for activity

Stage 2 – ALT is persistently above 50
but your LFT’s are Normal

Means you have an active hepatitis infection which over decades can cause 

Fibrosis without additional toxins like alcohol or being overweight and is best treated at some point and slowed with a liver friendly diet

Your Liver Team should provide a Personalised Care Plan if

Stage 3 – ALT/AST/GGT are 50 to 200 

Usually means you have taken liver toxins that worsen viral hepatitis eg alcohol, barbiturates, 

benzodiazepines, anticonvulsants, warfarin, antidepressants, paracetamol, 

or you may also have fatty liver from obesity

Stage 4 – GGT /ALT are 50 to 200 and ALP is above 200

Liver cells are damaged Cirrhosis and Fibrosis have occurred, liver functions 

can fall, tumours can occur. The author of this site was diagnosed in this stage 12 years ago,

point being a liver friendly diet, treatment and he is fine now.

The norm of ALT and AST levels in a blood test in women: what you need to know?

Contents

• 1 ALT and AST norms in women’s blood tests
  • 1.1 Women’s blood tests
  • 1.2 What are ALT and AST?
  • 1.3 The value of ALT and AST in the blood test
  • 1.4 Normal levels of ALT and AST in women
  • 1.5 The effect of age on the level of ALT and AST
  • 1.6 Causes of elevated levels of ALT and AST
  • 1.7 Liver disease and ALT and AST levels
  • 1.8 Cardiovascular disease and ALT and AST levels
  • 1.9 Causes of low ALT and AST levels
  • 1.10 Related videos:
  • 1.11 Q&A:
    • 9000 5 1.11.0.1 What are ALT and AST?
      • 1.11.0.2 Why do I need to measure blood levels of ALT and AST?
      • 1.11.0.3 What are the ALT and AST norms for women?
  • 1. 12 Liver disease and low ALT and AST levels
  • 1.13 Vitamin deficiency and low ALT and AST levels

The norm of the level of ALT (alanine aminotransferase) and AST (aspartate aminotransferase) in the blood test in women. What values ​​are considered normal and what may indicate deviations from the norm. Important indicators for diagnosing the condition of the liver and heart.

ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are enzymes that are found inside liver and heart cells. They play an important role in the metabolism of amino acids and are involved in the process of energy formation. The study of the levels of ALT and AST in the blood test reveals the presence and extent of damage to these organs.

Normal values ​​of ALT and AST are somewhat different in men and women, due to differences in body physiology. On average, in women, the acceptable level of ALT is from 7 to 35 units per liter, and the level of AST is from 7 to 31 units per liter of blood.

Elevated levels of ALT and AST may be indicative of various diseases and conditions. For example, elevated ALT levels may be associated with liver disease such as hepatitis or cirrhosis, and AST levels may be elevated with myocardial infarction or heart failure. However, elevated values ​​of these enzymes can also indicate other problems in the body, so diagnosis always requires an integrated approach and additional research.

Blood test for women

Blood test is one of the most common and informative laboratory procedures for assessing women’s health. It allows you to identify various deviations and pathologies, as well as monitor the effectiveness of treatment.

One of the key indicators in the blood test are the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). These enzymes are found in the cells of the liver and heart, respectively, and an increase in them may indicate problems with these organs.

Normal blood levels of ALT and AST in women depend on age and health status. Typically, ALT levels do not exceed 31 U/L and AST levels do not exceed 35 U/L. However, it must be taken into account that these indicators may vary depending on the laboratory and the research method.

Elevated ALT and AST levels in a woman’s blood test can be due to various causes, including liver disease (hepatitis, cirrhosis), heart disease (heart attack, angina pectoris), as well as the use of certain drugs or an alcohol disorder.

For women, regular blood testing is an important tool for maintaining health and preventing serious illness. In case of detection of deviations in the levels of ALT and AST, it is necessary to consult a doctor for additional studies and diagnosis.

What are ALT and AST?

ALT and AST are shorthand for enzymes called alanine aminotransferase (ALT) and aspartate aminotransferase (AST). They are present inside the cells of organs, especially in the liver, heart, muscles and kidneys. Blood levels of ALT and AST can be used to assess the function of these organs.

ALT and AST are enzymes that play a key role in amino acid metabolism in the body. ALT is responsible for the transfer of the amino group from alanine to alpha-ketoglutarate, and AST from aspartate to alpha-ketoglutarate. These enzymes are an integral part of the process of amino acid metabolism and energy metabolism in the body.

ALT and AST are located inside the cells of organs and usually they practically do not penetrate into the blood. However, when cells are damaged, the levels of these enzymes can increase and enter the bloodstream. Elevated ALT levels may indicate liver damage, while elevated AST levels may indicate damage to the liver, heart, or muscles.

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The value of ALT and AST in the blood test

ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are enzymes that are found inside the cells of organs, especially the liver and heart. When cell integrity is compromised, these enzymes are released into the blood.

ALT and AST can be used to determine the presence or extent of organ damage. Usually, their levels are markedly increased in the presence of liver diseases such as hepatitis or cirrhosis, as well as in heart disease and muscle damage.

ALT and AST values ​​in a blood test can be expressed in different units, but they are usually expressed in units per liter (U/L) or international activity units (IU/L). Normal ALT and AST values ​​depend on the laboratory performing the analysis and may differ in different countries and medical institutions.

In general, normal levels of ALT and AST in a blood test for women may be as follows:

• ALT: 7-35 U/L
• AST: 10-30 U/L

However, it is important to note that normal values ​​may differ slightly depending on the technique used in the laboratory, so the doctor’s advice should be taken into account when interpreting the results.

If the levels of ALT and AST in the blood test exceed the norm, this may indicate the presence of a pathological process in the liver, heart or other organs. In this case, the doctor may prescribe additional studies to determine the cause of the increase in these enzymes.

Normal levels of ALT and AST in women

ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are enzymes that are found inside the cells of various organs, including the liver, heart, muscles, kidneys and others. The level of these enzymes in the blood can indicate the condition of these organs.

Normal ALT levels in women vary by analysis and lab, but typically range from 7 to 35 units per litre. Elevated ALT levels can indicate various liver problems such as hepatitis, cirrhosis, or other diseases.

Normal AST levels in women can also vary depending on the analysis, but are usually between 5 and 40 units per liter. Elevated AST levels can indicate a variety of problems, including heart and muscle disease, and liver or kidney damage.

If ALT and AST levels in a woman’s blood are higher than normal, it is recommended to see a doctor for an examination and find out the cause. Diagnosis of the underlying disease that caused the increase in ALT and AST levels will allow prescribing effective treatment and preventing possible complications.

Effect of age on ALT and AST levels

Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) blood levels in women may vary with age. With age, there is often a gradual increase in the levels of these enzymes.

ALT and AST levels may increase in women over 40 due to age-related changes in the body. This is due to the deterioration of metabolic processes, changes in the functional activity of the liver and muscles.

ALT and AST levels can also be affected by age due to various diseases that can occur with age. Some diseases, such as cirrhosis of the liver, hepatitis, cholecystitis and other pathologies of the biliary tract, can lead to an increase in the level of ALT and AST.

It should be noted that the level of ALT and AST may vary depending on the individual characteristics of the woman. Therefore, when analyzing blood, it is necessary to take into account age, general condition of the body and other factors that can affect the level of these enzymes.

Causes of elevated levels of ALT and AST

Elevated levels of ALT and AST in the blood test in women can be caused by various reasons. This may be due to damage to cells in the liver, heart, muscles, or other organs.

One of the most common causes of elevated ALT and AST levels is liver disease such as cirrhosis or hepatitis. In these diseases, liver cells are damaged and the level of ALT and AST in the blood increases significantly.

Also elevated levels of ALT and AST can be caused by heart problems such as myocardial infarction or heart failure. When the heart muscle is damaged, more ALT and AST are released, which leads to their increase in the blood.

Other causes of elevated ALT and AST levels include the use of certain drugs, alcohol or drug poisoning, mechanical damage to organs or muscles, infectious diseases, and certain genetic disorders.

It is important to note that elevated ALT and AST levels do not always indicate a serious problem and may be temporary or caused by minor causes. However, if elevated levels of ALT and AST persist, it is necessary to consult a doctor for further examination and clarification of the cause.

Liver disease and ALT and AST levels

Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are enzymes that are found in high concentrations in liver cells. With the development of various liver diseases, such as hepatitis, cirrhosis, fatty degeneration, and others, the levels of ALT and AST can increase significantly.

However, an increase in ALT and AST may not always indicate the presence of a disease. The levels of these enzymes can also be elevated in the event of injury, certain medications, strenuous exercise, and even after drinking alcohol.

To determine the state of the liver and diagnose possible diseases, in addition to ALT and AST levels, a comprehensive blood test is usually performed, including the assessment of other indicators, such as levels of bilirubin, gamma-glutamyl transferase (GGT), alkaline phosphatase, and the diagnostic role of which is also very important.

When ALT and AST levels are abnormal, your doctor may recommend additional tests such as liver ultrasound, Liverscan, liver biopsy, and others. It is important to remember that it is impossible to draw final conclusions about the state of the liver only by the levels of ALT and AST, a comprehensive assessment of all indicators and a medical opinion are required.

Therefore, if you have elevated levels of ALT and AST, do not panic, see a doctor who can diagnose and identify the cause of such changes. Medical care and timely access to a doctor play an important role in assessing the condition of the liver and preventing possible complications.

Cardiovascular disease and ALT and AST levels

Cardiovascular disease is one of the leading causes of death among women worldwide. Often these diseases do not have pronounced symptoms in the early stages, so it is important to regularly monitor your health and conduct tests, including ALT and AST levels.

ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are enzymes found in various organs, including the liver and heart. If these organs are damaged, the levels of ALT and AST can increase significantly, indicating the presence of pathological processes.

The level of ALT in a blood test is an indicator of liver function. With defects and damage to the liver cells, such as cirrhosis or hepatitis, ALT may increase. In addition, elevated ALT levels may indicate the presence of heart failure, which often develops against the background of cardiovascular disease.

At the same time, AST levels can also be an indicator of heart disease. An increase in AST may indicate the presence of myocardial infarction or acute coronary syndrome. However, a simple increase in the level of AST is not a specific indicator of cardiovascular disease, so additional examination is required to clarify the diagnosis.

Thus, the control of ALT and AST levels in the blood test is an important step in the diagnosis of cardiovascular diseases in women. Elevated values ​​of these enzymes may indicate the presence of a pathology, however, an integrated approach and additional examination are required to make an accurate diagnosis and prescribe treatment.

Causes of low levels of ALT and AST

Low levels of ALT (alanine aminotransferase) and AST (aspartate aminotransferase) in the blood test can indicate various diseases and conditions in the body of women.

1. Liver failure: Low levels of ALT and AST may indicate serious liver problems. This may be due to cirrhosis of the liver, chronic hepatitis, hepatic necrosis, or other liver pathologies.

2. Heart disease: Low AST levels may be associated with heart disease such as myocardial infarction, heart failure, or arrhythmias. This is due to the fact that AST is contained in the mitochondria of the heart muscle and its decrease may indicate damage to the heart tissue.

3. Vitamin deficiency: Low levels of ALT and AST may be due to a lack of important vitamins such as vitamin B6 and vitamin B12. Deficiency of these vitamins can cause abnormalities in the functioning of the liver and heart, which leads to a decrease in the levels of ALT and AST in the blood.

4. Individual features: Some women have low levels of ALT and AST in the blood up to the physiological norm. This may be due to the peculiarities of their metabolism or genetic factors. In such cases, low levels of ALT and AST are usually not dangerous and do not require additional examination or treatment.

It is important to note that low levels of ALT and AST in the blood test require further investigation and consultation with a physician. Only he can determine the specific cause of such changes and prescribe the necessary treatment or observation.

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Q&A:

What are ALT and AST?

ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are enzymes found in the cells of the liver, heart, muscles, and other organs. They specifically process certain amino acids and help in converting them into energy for the body to work.

Why is it necessary to measure ALT and AST levels in the blood?

ALT and AST blood levels can be used to evaluate the condition of the liver and other organs such as the heart and muscles. Elevated levels of these enzymes may indicate the presence of inflammation or damage to the cells in these organs.

What are the ALT and AST norms for women?

Normal blood levels of ALT and AST may vary slightly between laboratories depending on the methods used. In general, normal ALT levels usually do not exceed 30 U/L and AST levels do not exceed 34 U/L. However, for an accurate interpretation of the results, it is best to consult a doctor who knows the patient’s history and can take into account other factors.

Liver disease and low ALT and AST levels

ALT (alanine aminotransferase) and AST (aspartate aminotransferase) blood values ​​are important indicators of liver function. They help determine the presence or absence of damage to the organ. In some liver diseases, however, ALT and AST levels may be low or normal, which can be difficult to diagnose.

One cause of low ALT and AST may be liver atrophy. With this disease, the volume of the liver decreases, which leads to a decrease in the activity of enzymes. Another possible cause of low levels of ALT and AST is cirrhosis of the liver, which is characterized by the replacement of healthy organ tissue with scarring. In this case, the number of liver cells that produce ALT and AST decreases, which leads to low levels of these enzymes in the blood.

In addition to atrophy and cirrhosis of the liver, low levels of ALT and AST may be associated with the presence of diseases for the first time that can suppress the functioning of the organ. These diseases include hepatitis and fatty degeneration of the liver. In these pathologies, inflammation and accumulation of lipids in the liver are present, which leads to a decrease in the activity of ALT and AST. This, in turn, may indicate the presence of a progression of the disease or a reactive state of the body.

It is important to note that low levels of ALT and AST are not specific signs of specific liver diseases and may be symptoms of various pathologies. Additional studies and analyzes are needed for an accurate diagnosis. Blood test results should be interpreted in the light of other clinical findings and in consultation with the physician.

Vitamin deficiencies and low levels of ALT and AST

A significant decrease in the levels of ALT and AST in the blood test in women may be associated with a vitamin deficiency. Vitamins are important trace elements necessary for the normal functioning of the body. They are catalysts for many biochemical reactions, including those that regulate ALT and AST levels.

Deficiency of certain vitamins can lead to decreased activity of these enzymes. For example, a lack of vitamin B6 may be associated with low levels of ALT and AST. Vitamin B6 plays an important role in the metabolism of amino acids, which form the basis of proteins, including ALT and AST.

Vitamin C deficiency may also be associated with low levels of ALT and AST. Vitamin C is involved in the synthesis of collagen, which strengthens the walls of blood vessels. Its deficiency can lead to liver damage and lower ALT and AST levels.

In general, low ALT and AST levels associated with vitamin deficiencies may indicate organ and system dysfunction. You need to pay attention to your diet and ensure that you are getting enough of all the essential vitamins to maintain normal ALT and AST levels and overall body health.

ALT (ALT, Alanine aminotransferase, alanine transaminase, SGPT, Alanine aminotransferase)

Alanine aminotransferase (AlAT, ALT) is an intracellular enzyme, the content of which in the blood of healthy people is low. It is mainly found in the cells of the liver, myocardium, skeletal muscles, pancreas. When cells containing ALT are damaged or destroyed, the enzyme is released into the bloodstream, and its concentration in the blood increases.

Determination of the level of alanine aminotransferase is carried out for the diagnosis of liver diseases and dynamic monitoring of their treatment. The analysis is performed for suspected acute or chronic hepatitis of viral or toxic etiology, cirrhosis of the liver, primary tumors, or metastatic liver disease.

The growth of alanine aminotransferase in the blood in hepatitis is noted much earlier than the onset of the icteric stage, which makes it possible to identify the pathology at the initial stage.

As part of a screening examination (preventive examination of persons who do not have complaints) to assess the state of the liver, before planned hospitalization and surgical treatment, an analysis for ALT is prescribed together with another enzyme – AsAT (aspartate aminotransferase).

The level of ALT together with other enzymes is evaluated in diseases of the pancreas and gallbladder – pancreatitis, cholecystitis, cholelithiasis; if there are complaints of unexplained general weakness, fatigue, yellowness of the skin and sclera, abdominal pain, including a feeling of heaviness in the right hypochondrium, nausea, vomiting.

In addition, the ALT level is taken into account in myocardial infarction and myocarditis, although in cases of heart damage it is only of secondary importance. The study is prescribed for suspected myositis, myodystrophy, when complaints of muscle pain cannot be explained by injuries or excessive physical activity.

Donation is a mandatory reason for testing for ALT.

ALT values ​​are assessed in any chronic disease, before prescribing drug therapy, for example, antitumor, anti-tuberculosis drugs, to assess the initial state of the liver and over time to assess drug tolerance.

Preparation for the procedure

It is better to take the test in the morning on an empty stomach (after an 8-14 hour break after the last meal).

Drinking water is allowed.

If necessary, it is permissible to donate blood 4-6 hours after a light meal.

On the eve it is desirable to avoid physical and emotional overload, overeating.

Avoid alcohol intake 5-6 days before the test.

Avoid smoking 30 minutes before blood sampling.

Deadline

The survey is completed within one business day.

What can affect the results

Intense physical activity the day before and even a few days before the test can lead to damage to muscle tissue (the so-called tear of muscle fibers) and, accordingly, an increase in the level of ALT. For the same reason, the analysis given after the injury is not informative.

Taking alcohol, certain drugs (antibiotics, non-steroidal anti-inflammatory drugs, anticancer drugs, oral contraceptives, etc.) often distort the result of the study. The list of medications taken should be discussed with the doctor who ordered the analysis, cancel those that are possible – without risk to health.

ALT (ALT, Alanine aminotransferase, alanine transaminase)

For research, blood is taken from a vein. Usually, ASAT (AST, Aspartate aminotransferase) is determined simultaneously and the ratio of ASAT / AlAT (de Ritis coefficient) is estimated.

You can take a blood test for ALT (ALT, Alanine aminotransferase, alanine transaminase) at the nearest INVITRO medical office. The list of offices where biomaterial is accepted for laboratory testing is presented in the “Addresses” section.

Interpretation of test results contains information for the attending physician and is not a diagnosis. The information in this section should not be used for self-diagnosis or self-treatment. An accurate diagnosis is made by the doctor, using both the results of this examination and the necessary information from other sources: history, results of other examinations, etc.

Normal

Units of measure: U/l.

Reference values ​​

Explanation of indicators

The level of ALT depends on the age and sex of the patient. Minor deviations from the norm, as a rule, do not require drug therapy, and the recommendations associated with them, such as rational nutrition, avoidance of alcohol, etc. should be discussed with your doctor.

The AST/ALAT ratio (de Ritis ratio) is normally between 0.91 and 1.75.

What do low readings mean

A significant decrease in the level of ALT can be detected in severe liver damage, for example, in the terminal stage of liver cirrhosis, when the number of liver cells is significantly reduced.

What do elevated readings mean

First of all, with an increase in ALT, liver problems should be suspected: fatty hepatosis, hepatitis of viral or toxic etiology, cirrhosis of the liver, liver cancer – primary or metastatic.

The degree of increase in ALT is usually associated with the extent or severity of liver damage, but cannot be considered as a determining factor for the prognosis of the disease. The maximum levels of ALT (and AST) – more than a hundred times higher than the norm, are observed in patients with acute viral and drug-induced hepatitis.

A significant increase in alanine aminotransferase can be observed in acute cholecystitis, cholelithiasis, and acute destructive pancreatitis. Another reason may be the use of hepatotoxic drugs that damage liver cells.

An increase in the level of ALT is detected with extensive injuries of the skeletal muscles, severe myositis and myodystrophy, frequent intramuscular injections.

A less significant increase in ALT is recorded in acute myocardial infarction and myocarditis.

Additional examination in case of deviation of the indicator from the norm

If a change (often an increase) in the level of ALT is detected, patients are consulted

general practitioners

,

gastroenterologists

, hepatologists, infectious disease specialists.

To clarify the diagnosis, in addition to ALT, other liver enzymes (AST, gamma-HT, alkaline phosphatase, bilirubin), clinical blood counts, and markers of viral hepatitis, primarily hepatitis B and hepatitis C, are usually examined.

An ultrasound examination of the abdominal organs is performed, according to indications – computed tomography (CT) with contrast.

If damage to the skeletal muscles is suspected, the CPK enzyme is additionally examined and a rheumatologist is consulted.

If there is a suspicion of damage to the heart muscle, a consultation with a cardiologist is required. Usually, the doctor prescribes additional electrocardiography (ECG), echocardiography, blood test for CF-CPK, troponin I.

O.P. The role of new reference values ​​of alanine aminotransferase in the diagnosis of various forms of non-alcoholic fatty liver disease in patients with metabolic syndrome. Journal of Biomedical Technologies № 1. 2015. P. 9-15.

Clinical guidelines “Liver cancer (hepatocellular)”. Developed by: Association of Oncologists of Russia, Russian Society of Clinical Oncology, Russian Society of Radiologists and Radiologists.