What is a normal A1C level. How often should you get an A1C test. What factors can affect your A1C result. How to interpret your A1C results for diabetes management.

What is the A1C Test and Why is it Important?

The A1C test, also known as the hemoglobin A1C or HbA1c test, is a crucial tool in diagnosing and managing diabetes. It provides a comprehensive view of your blood sugar levels over the past three months, offering valuable insights into your overall glucose control.

How does the A1C test work? When sugar enters your bloodstream, it attaches to hemoglobin, a protein in your red blood cells. The A1C test measures the percentage of your red blood cells that have sugar-coated hemoglobin. This measurement gives healthcare providers a clear picture of your average blood sugar levels over an extended period.

The Importance of A1C in Diabetes Management

Why is the A1C test so significant in diabetes care? It serves multiple purposes:

• Diagnosis of prediabetes and diabetes
• Monitoring long-term blood sugar control
• Assessing the effectiveness of diabetes treatment plans
• Predicting the risk of diabetes-related complications

Regular A1C testing allows healthcare providers to make informed decisions about treatment adjustments and helps individuals with diabetes track their progress in managing the condition.

Normal A1C Levels and Interpreting Your Results

Understanding your A1C results is crucial for effective diabetes management. But what exactly constitutes a normal A1C level? Here’s a breakdown of A1C ranges and their interpretations:

• Normal: Below 5.7%
• Prediabetes: 5.7% to 6.4%
• Diabetes: 6.5% or above

It’s important to note that within the prediabetes range of 5.7% to 6.4%, higher A1C levels indicate a greater risk of developing type 2 diabetes. This information can be valuable for implementing preventive measures and lifestyle changes.

Estimated Average Glucose (eAG)

For individuals managing diabetes, A1C results can also be reported as estimated average glucose (eAG). This measurement provides a more familiar reference point, as it uses the same units (mg/dL) seen on blood sugar meters. Here’s a quick conversion guide:

Understanding both A1C percentages and eAG values can help individuals better interpret their results and set appropriate goals for blood sugar management.

Who Should Get an A1C Test and How Often?

Determining when and how often to get an A1C test depends on various factors, including your age, risk factors, and current health status. Here are some general guidelines:

Testing for Prediabetes or Diabetes

• Adults over 45: Get a baseline A1C test
• Adults under 45: Get tested if you’re overweight and have one or more risk factors for prediabetes or type 2 diabetes
• If your result is normal but you have risk factors: Repeat the test every 3 years
• If you have prediabetes: Get tested every 1 to 2 years, or as recommended by your doctor
• If your result indicates diabetes: Confirm with a second test on a different day

Managing Diagnosed Diabetes

For individuals with diagnosed diabetes, A1C testing should be more frequent:

• Get an A1C test at least twice a year
• Consider more frequent testing if your medication changes or you have other health conditions
• Consult with your healthcare provider to determine the optimal testing frequency for your specific situation

Regular A1C testing is crucial for tracking your progress and making necessary adjustments to your diabetes management plan.

Factors That Can Affect Your A1C Result

While the A1C test is generally reliable, several factors can influence the results, potentially leading to falsely high or low readings. It’s essential to be aware of these factors and discuss them with your healthcare provider:

Medical Conditions

• Kidney failure
• Liver disease
• Severe anemia

Genetic Factors

Certain hemoglobin variants, more common in people of African, Mediterranean, or Southeast Asian descent, can affect A1C results. Blood disorders such as sickle cell anemia or thalassemia may also impact the accuracy of the test.

Medications

Some medications can interfere with A1C results, including:

• Opioids
• Certain HIV medications

Other Factors

• Recent blood loss or blood transfusions
• Early or late pregnancy

If any of these factors apply to you, inform your healthcare provider. They may recommend additional tests to ensure accurate assessment of your blood sugar control.

Setting and Achieving Your A1C Goal

Establishing an appropriate A1C goal is a crucial step in effective diabetes management. While the general target for most people with diabetes is 7% or less, it’s important to recognize that A1C goals should be individualized based on various factors.

Factors Influencing A1C Goals

• Age
• Duration of diabetes
• Presence of other medical conditions
• Risk of hypoglycemia (low blood sugar)
• Individual health status and life expectancy

Younger individuals with diabetes may have lower A1C goals to reduce the long-term risk of complications. Conversely, older adults or those with severe hypoglycemia or other serious health issues may have higher A1C targets.

Collaborating with Your Healthcare Provider

How can you determine the most appropriate A1C goal for your situation? Work closely with your healthcare provider to establish a personalized target. This collaborative approach ensures that your goal is both achievable and beneficial for your overall health.

Remember that A1C goals may change over time as your health status or life circumstances evolve. Regular communication with your healthcare team is essential for adjusting your target as needed.

The Role of A1C in Comprehensive Diabetes Management

While the A1C test is a valuable tool in diabetes care, it’s important to understand its role within a broader diabetes management strategy. A1C provides an average of blood sugar levels over time, but it doesn’t capture the daily fluctuations that can impact your health and well-being.

Complementing A1C with Regular Blood Sugar Testing

Why is it crucial to combine A1C testing with regular blood sugar monitoring? Daily blood sugar testing offers several benefits:

• Provides real-time information on blood sugar levels
• Helps identify patterns and trends in blood sugar fluctuations
• Allows for immediate adjustments in diet, activity, or medication
• Assists in managing high or low blood sugar episodes

Two individuals can have the same A1C result but vastly different daily blood sugar patterns. Regular self-monitoring helps capture these variations and informs more precise diabetes management strategies.

When to Increase Blood Sugar Monitoring

In what situations should you consider more frequent blood sugar testing? If you’re reaching your A1C goal but experiencing symptoms of high or low blood sugar, it may be time to increase your monitoring. Keep a detailed log of your results and share them with your healthcare provider to guide any necessary adjustments to your treatment plan.

Leveraging A1C for Improved Diabetes Care

The A1C test is a powerful tool in the diabetes management toolkit, offering valuable insights into long-term blood sugar control. By understanding what A1C measures, how to interpret the results, and how it complements daily blood sugar monitoring, individuals with diabetes can take a more active role in their care.

Key Takeaways for Effective A1C Utilization

• Regular A1C testing as recommended by your healthcare provider
• Understanding your personal A1C goal and working towards it
• Combining A1C results with daily blood sugar monitoring for comprehensive care
• Open communication with your healthcare team about A1C results and any concerns
• Awareness of factors that may affect A1C accuracy

By integrating A1C testing into a holistic diabetes management approach, individuals can achieve better blood sugar control, reduce the risk of complications, and improve their overall quality of life. Remember that diabetes management is a journey, and the A1C test serves as a valuable guide along the way.

As research in diabetes care continues to advance, new insights and technologies may further enhance the role of A1C testing in diabetes management. Staying informed about these developments and maintaining an open dialogue with your healthcare provider will ensure that you’re always at the forefront of effective diabetes care.

All About Your A1C

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What has your blood sugar been up to lately? Get an A1C test to find out your average levels—important to know if you’re at risk for prediabetes or type 2 diabetes, or if you’re managing diabetes.

The A1C test—also known as the hemoglobin A1C or HbA1c test—is a simple blood test that measures your average blood sugar levels over the past 3 months. It’s one of the commonly used tests to diagnose prediabetes and diabetes, and is also the main test to help you and your health care team manage your diabetes. Higher A1C levels are linked to diabetes complications, so reaching and maintaining your individual A1C goal is really important if you have diabetes.

What Does the A1C Test Measure?

When sugar enters your bloodstream, it attaches to hemoglobin, a protein in your red blood cells. Everybody has some sugar attached to their hemoglobin, but people with higher blood sugar levels have more. The A1C test measures the percentage of your red blood cells that have sugar-coated hemoglobin.

Who Should Get an A1C Test, and When?

Testing for diabetes or prediabetes:
Get a baseline A1C test if you’re an adult over age 45—or if you’re under 45, are overweight, and have one or more risk factors for prediabetes or type 2 diabetes:

• If your result is normal but you’re over 45, have risk factors, or have ever had gestational diabetes, repeat the A1C test every 3 years.
• If your result shows you have prediabetes, talk to your doctor about taking steps now to improve your health and lower your risk for type 2 diabetes. Repeat the A1C test as often as your doctor recommends, usually every 1 to 2 years.
• If you don’t have symptoms but your result shows you have prediabetes or diabetes, get a second test on a different day to confirm the result.
• If your test shows you have diabetes, ask your doctor to refer you to diabetes self-management education and support services so you can have the best start in managing your diabetes.

Managing diabetes:
If you have diabetes, get an A1C test at least twice a year, more often if your medicine changes or if you have other health conditions. Talk to your doctor about how often is right for you.

How to Prepare for Your A1C Test

The test is done in a doctor’s office or a lab using a sample of blood from a finger stick or from your arm. You don’t need to do anything special to prepare for your A1C test. However, ask your doctor if other tests will be done at the same time and if you need to prepare for them.

Your A1C Result

Diagnosing Prediabetes or Diabetes

A normal A1C level is below 5.7%, a level of 5. 7% to 6.4% indicates prediabetes, and a level of 6.5% or more indicates diabetes. Within the 5.7% to 6.4% prediabetes range, the higher your A1C, the greater your risk is for developing type 2 diabetes.

Managing Diabetes
Your A1C result can also be reported as estimated average glucose (eAG), the same numbers (mg/dL) you’re used to seeing on your blood sugar meter:

What Can Affect Your A1C Result?

Get your A1C tested in addition to—not instead of—regular blood sugar self-testing if you have diabetes.

Several factors can falsely increase or decrease your A1C result, including:

• Kidney failure, liver disease, or severe anemia.
• A less common type of hemoglobin that people of African, Mediterranean, or Southeast Asian descent and people with certain blood disorders (such as sickle cell anemia or thalassemia) may have.
• Certain medicines, including opioids and some HIV medications.
• Blood loss or blood transfusions.
• Early or late pregnancy.

Let your doctor know if any of these factors apply to you, and ask if you need additional tests to find out.

Your A1C Goal

The goal for most people with diabetes is 7% or less. However, your personal goal will depend on many things such as your age and any other medical conditions. Work with your doctor to set your own individual A1C goal.

Younger people have more years with diabetes ahead, so their goal may be lower to reduce the risk of complications, unless they often have hypoglycemia (low blood sugar, or a “low”). People who are older, have severe lows, or have other serious health problems may have a higher goal.

A1C: Just Part of the Toolkit

A1C is an important tool for managing diabetes, but it doesn’t replace regular blood sugar testing at home. Blood sugar goes up and down throughout the day and night, which isn’t captured by your A1C. Two people can have the same A1C, one with steady blood sugar levels and the other with high and low swings.

If you’re reaching your A1C goal but having symptoms of highs or lows, check your blood sugar more often and at different times of day. Keep track and share the results with your doctor so you can make changes to your treatment plan if needed.

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The A1C Test & Diabetes

On this page:

• What is the A1C test?
• Why should a person get the A1C test?
• How is the A1C test used to diagnose type 2 diabetes and prediabetes?
• Is the A1C test used during pregnancy?
• Can other blood glucose tests be used to diagnose type 2 diabetes and prediabetes?
• Can the A1C test result in a different diagnosis than the blood glucose tests?
• Why do diabetes blood test results vary?
• How precise is the A1C test?
• How is the A1C test used after diagnosis of diabetes?
• What A1C goal should I have?
• How does A1C relate to estimated average glucose?
• Will the A1C test show short-term changes in blood glucose levels?
• Clinical Trials for the A1C Test and Diabetes

What is the A1C test?

The A1C test is a blood test that provides information about your average levels of blood glucose, also called blood sugar, over the past 3 months. The A1C test can be used to diagnose type 2 diabetes and prediabetes.¹ The A1C test is also the primary test used for diabetes management.

An A1C test is a blood test that reflects your average blood glucose levels over the past 3 months.

The A1C test is sometimes called the hemoglobin A1C, HbA1c, glycated hemoglobin, or glycohemoglobin test. Hemoglobin is the part of a red blood cell that carries oxygen to the cells. Glucose attaches to or binds with hemoglobin in your blood cells, and the A1C test is based on this attachment of glucose to hemoglobin.

The higher the glucose level in your bloodstream, the more glucose will attach to the hemoglobin. The A1C test measures the amount of hemoglobin with attached glucose and reflects your average blood glucose levels over the past 3 months.

The A1C test result is reported as a percentage. The higher the percentage, the higher your blood glucose levels have been. A normal A1C level is below 5.7 percent.

Why should a person get the A1C test?

Testing can help health care professionals

• find prediabetes and counsel you about lifestyle changes to help you delay or prevent type 2 diabetes
• find type 2 diabetes
• work with you to monitor the disease and help make treatment decisions to prevent complications

If you have risk factors for prediabetes or diabetes, talk with your doctor about whether you should be tested.

You may be able to prevent or delay type 2 diabetes with lifestyle changes such as weight loss or being physically active most days of the week.

How is the A1C test used to diagnose type 2 diabetes and prediabetes?

Health care professionals can use the A1C test alone or in combination with other diabetes tests to diagnose type 2 diabetes and prediabetes. You don’t have to fast before having your blood drawn for an A1C test, which means that blood can be drawn for the test at any time of the day.

If you don’t have symptoms but the A1C test shows you have diabetes or prediabetes, you should have a repeat test on a different day using the A1C test or one of the other diabetes tests to confirm the diagnosis.²

A1C results and what the numbers mean

*Any test used to diagnose diabetes requires confirmation with a second measurement, unless there are clear symptoms of diabetes.

Diagnosis*	A1C Level
Normal	below 5. 7 percent
Prediabetes	5.7 to 6.4 percent
Diabetes	6.5 percent or above

When using the A1C test for diagnosis, your doctor will send your blood sample taken from a vein to a lab that uses an NGSP-certified method. The NGSP, formerly called the National Glycohemoglobin Standardization Program, certifies that makers of A1C tests provide results that are consistent and comparable with those used in the Diabetes Control and Complications Trial.

Blood samples analyzed in a doctor’s office or clinic, known as point-of-care tests, should not be used for diagnosis.

The A1C test should not be used to diagnose type 1 diabetes, gestational diabetes, or cystic fibrosis-related diabetes. The A1C test may give false results in people with certain conditions.

Having prediabetes is a risk factor for developing type 2 diabetes. Within the prediabetes A1C range of 5. 7 to 6.4 percent, the higher the A1C, the greater the risk of diabetes.

Is the A1C test used during pregnancy?

Health care professionals may use the A1C test early in pregnancy to see if a woman with risk factors had undiagnosed diabetes before becoming pregnant. Since the A1C test reflects your average blood glucose levels over the past 3 months, testing early in pregnancy may include values reflecting time before you were pregnant. The glucose challenge test or the oral glucose tolerance test (OGTT) are used to check for gestational diabetes, usually between 24 and 28 weeks of pregnancy. If you had gestational diabetes, you should be tested for diabetes no later than 12 weeks after your baby is born. If your blood glucose is still high, you may have type 2 diabetes. Even if your blood glucose is normal, you still have a greater chance of developing type 2 diabetes in the future and should get tested every 3 years.

Can other blood glucose tests be used to diagnose type 2 diabetes and prediabetes?

Yes. Health care professionals also use the fasting plasma glucose (FPG) test and the OGTT to diagnose type 2 diabetes and prediabetes. For these blood glucose tests used to diagnose diabetes, you must fast at least 8 hours before you have your blood drawn. If you have symptoms of diabetes, your doctor may use the random plasma glucose test, which doesn’t require fasting. In some cases, health care professionals use the A1C test to help confirm the results of another blood glucose test.

Can the A1C test result in a different diagnosis than the blood glucose tests?

Yes. In some people, a blood glucose test may show diabetes when an A1C test does not. The reverse can also occur—an A1C test may indicate diabetes even though a blood glucose test does not. Because of these differences in test results, health care professionals repeat tests before making a diagnosis.

People with differing test results may be in an early stage of the disease, when blood glucose levels have not risen high enough to show up on every test. In this case, health care professionals may choose to follow the person closely and repeat the test in several months.

Why do diabetes blood test results vary?

Lab test results can vary from day to day and from test to test. This can be a result of the following factors:

Blood glucose levels move up and down

Your results can vary because of natural changes in your blood glucose level. For example, your blood glucose level moves up and down when you eat or exercise. Sickness and stress also can affect your blood glucose test results. A1C tests are less likely to be affected by short-term changes than FPG or OGTT tests.

The following chart shows how multiple blood glucose measurements over 4 days compare with an A1C measurement.

Blood Glucose Measurements Compared with A1C Measurements over 4 Days

Blood glucose (mg/dL) measurements were taken four times per day (fasting or pre-breakfast, pre-lunch, pre-dinner, and bedtime).

The straight black line shows an A1C measurement of 7. 0 percent. The blue line shows an example of how blood glucose test results might look from self-monitoring four times a day over a 4-day period.

A1C tests can be affected by changes in red blood cells or hemoglobin

Conditions that change the life span of red blood cells, such as recent blood loss, sickle cell disease, erythropoietin treatment, hemodialysis, or transfusion, can change A1C levels.

A falsely high A1C result can occur in people who are very low in iron; for example, those with iron-deficiency anemia. Other causes of false A1C results include kidney failure or liver disease.

If you’re of African, Mediterranean, or Southeast Asian descent or have family members with sickle cell anemia or a thalassemia, an A1C test can be unreliable for diagnosing or monitoring diabetes and prediabetes. People in these groups may have a different type of hemoglobin, known as a hemoglobin variant, which can interfere with some A1C tests. Most people with a hemoglobin variant have no symptoms and may not know that they carry this type of hemoglobin. Health care professionals may suspect interference—a falsely high or low result—when your A1C and blood glucose test results don’t match.

If you’re of African, Mediterranean, or Southeast Asian descent, you could have a different type of hemoglobin that affects your diabetes care.

Not all A1C tests are unreliable for people with a hemoglobin variant. People with false results from one type of A1C test may need a different type of A1C test to measure their average blood glucose level. The NGSP provides information for health care professionals about which A1C tests are appropriate to use for specific hemoglobin variants.

Read about diabetes blood tests for people of African, Mediterranean, or Southeast Asian descent. The NIDDK has information for health care providers on Sickle Cell Trait & Other Hemoglobinopathies & Diabetes.

Small changes in temperature, equipment, or sample handling

Even when the same blood sample is repeatedly measured in the same lab, the results may vary because of small changes in temperature, equipment, or sample handling. These factors tend to affect glucose measurements—fasting and OGTT—more than the A1C test.

Your health care professional can help you understand your test results.

Health care professionals understand these variations and repeat lab tests for confirmation. Diabetes develops over time, so even with variations in test results, health care professionals can tell when overall blood glucose levels are becoming too high.

How precise is the A1C test?

When repeated, the A1C test result can be slightly higher or lower than the first measurement. This means, for example, an A1C reported as 6.8 percent on one test could be reported in a range from 6.4 to 7.2 percent on a repeat test from the same blood sample.³ In the past, this range was larger but new, stricter quality-control standards mean more precise A1C test results.

Health care professionals can visit ngsp.org to find information about the precision of the A1C test used by their lab.

How is the A1C test used after diagnosis of diabetes?

Your health care professional may use the A1C test to set your treatment goals, modify therapy, and monitor your diabetes management.

Experts recommend that people with diabetes have an A1C test at least twice a year.⁴ Health care professionals may check your A1C more often if you aren’t meeting your treatment goals.⁴

What A1C goal should I have?

People will have different A1C targets, depending on their diabetes history and their general health. You should discuss your A1C target with your health care professional. Studies have shown that some people with diabetes can reduce the risk of diabetes complications by keeping A1C levels below 7 percent.

Managing blood glucose early in the course of diabetes may provide benefits for many years to come. However, an A1C level that is safe for one person may not be safe for another. For example, keeping an A1C level below 7 percent may not be safe if it leads to problems with hypoglycemia, also called low blood glucose.

Less strict blood glucose control, or an A1C between 7 and 8 percent—or even higher in some circumstances—may be appropriate in people who have

• limited life expectancy
• long-standing diabetes and trouble reaching a lower goal
• severe hypoglycemia or inability to sense hypoglycemia (also called hypoglycemia unawareness)
• advanced diabetes complications such as chronic kidney disease, nerve problems, or cardiovascular disease

How does A1C relate to estimated average glucose?

Estimated average glucose (eAG) is calculated from your A1C. Some laboratories report eAG with A1C test results. The eAG number helps you relate your A1C to daily glucose monitoring levels. The eAG calculation converts the A1C percentage to the same units used by home glucose meters—milligrams per deciliter (mg/dL).

The eAG number will not match daily glucose readings because it’s a long-term average—rather than your blood glucose level at a single time, as is measured with a home glucose meter.

Will the A1C test show short-term changes in blood glucose levels?

Large changes in your blood glucose levels over the past month will show up in your A1C test result, but the A1C test doesn’t show sudden, temporary increases or decreases in blood glucose levels. Even though A1C results represent a long-term average, blood glucose levels within the past 30 days have a greater effect on the A1C reading than those in previous months.

Clinical Trials for the A1C Test and Diabetes

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and other components of the National Institutes of Health (NIH) conduct and support research into many diseases and conditions.

What are clinical trials and are they right for you?

Clinical trials are part of clinical research and at the heart of all medical advances. Clinical trials look at new ways to prevent, detect, or treat disease. Scientists are conducting research to learn more about diabetes, including studies about A1C. For example

• how the relationship between A1C and blood glucose may vary in different racial and ethnic groups
• to find other tests that may be better than A1C for some people
• to look for ways to further improve A1C test results. Because the A1C value depends on the average life span of your red blood cells, knowing whether the life span of your red blood cells is longer or shorter may give your doctor helpful information.

Researchers also use clinical trials to look at other aspects of care, such as improving the quality of life for people with chronic illnesses. Find out if clinical trials are right for you.

What clinical trials are open?

Clinical trials that are currently open and are recruiting can be viewed at www. ClinicalTrials.gov.

References

Glycated hemoglobin (HbA1c)

Glycated hemoglobin (A1c) is a specific compound of erythrocyte hemoglobin with glucose, the concentration of which reflects the average blood glucose over a period of about three months.

Synonyms Russian

Glycohemoglobin, hemoglobin A1c, Hb _A1c , glycosylated hemoglobin.

English synonyms

Glycated hemoglobin, hemoglobin A1c, HbA1c, glycohemoglobin, glycosylated hemoglobin.

Test method *

Ion exchange high performance liquid chromatography (HPLC).

* Method may vary in some regions.

Units

% (percentage).

What biomaterial can be used for research?

Venous blood.

How to properly prepare for an examination?

• Do not eat for 2-3 hours before the examination, you can drink pure non-carbonated water.
• Exclude physical and emotional overexertion within 30 minutes prior to the study.
• Do not smoke for 30 minutes before the test.

Overview of the study

The glycated hemoglobin (A1c) test helps to assess the average blood glucose level over the past 2-3 months.

Hemoglobin is an oxygen-carrying protein found inside red blood cells (erythrocytes). There are several types of normal hemoglobin, and many abnormal varieties have been identified, although the predominant form is hemoglobin A, which is 95-98% of total hemoglobin. Hemoglobin A is divided into several components, one of which is A1c. Part of the glucose circulating in the blood spontaneously binds to hemoglobin, forming the so-called glycated hemoglobin. The higher the concentration of glucose in the blood, the more glycated hemoglobin is formed. Having combined with hemoglobin, glucose remains “in conjunction” with it until the very end of the life of the erythrocyte, that is, 120 days. The combination of glucose with hemoglobin A is called HbA1c or A1c. Glycated hemoglobin is formed in the blood and disappears from it every day, as old red blood cells die, and young (not yet glycated) take their place.

The hemoglobin A1c test is used to monitor the condition of patients diagnosed with diabetes mellitus. It helps to assess how effectively the regulation of glucose levels during treatment is going on.

For some patients, a hemoglobin A1c test is prescribed to diagnose diabetes and pre-diabetes in addition to a fasting plasma glucose test and a glucose tolerance test.

The resulting value is measured as a percentage. Patients with diabetes should strive to keep their glycated hemoglobin levels below 7%.

A1c should be reported in one of three ways:

• as a percentage of total hemoglobin,
• in mmol/mol, according to the International Federation of Clinical Chemistry and Laboratory Medicine,
• as mean glucose mg/dl or mmol/l.

What is research used for?

• For the control of glucose in patients with diabetes mellitus – for them to maintain its level in the blood as close to normal as possible is very important. This helps to minimize complications to the kidneys, eyes, cardiovascular and nervous systems.
• To determine the patient’s average blood glucose over the past few months.
• To validate the correctness of the measures taken for the treatment of diabetes and to find out if they need to be adjusted.
• To detect uncontrolled rises in blood glucose in patients with newly diagnosed diabetes mellitus. Moreover, the test may be prescribed several times until the desired glucose level is detected, then it needs to be repeated several times a year to make sure that the normal level is maintained.
• For preventive purposes, to diagnose diabetes at an early stage.

When is the test ordered?

Depending on the type of diabetes and how well the disease is treated, A1c is tested 2 to 4 times a year. On average, patients with diabetes are recommended to be tested for A1c twice a year. If the patient is diagnosed with diabetes for the first time or the control measurement fails, the analysis is re-assigned.

In addition, this test is ordered if the patient is suspected of having diabetes because there are symptoms of high blood glucose:

• extreme thirst,
• frequent copious urination,
• fatigue,
• blurred vision,
• increased susceptibility to infections.

What do the results mean?

Reference values: * 4.27 – 6.07%.

*Reference values ​​vary for some regions due to the use of different test systems for the study.

The closer the A1c level is to 7% in a diabetic patient, the easier it is to control the disease. Accordingly, with an increase in the level of glycated hemoglobin, the risk of complications also increases.

The results of the analysis for A1c are interpreted as follows.

According to the clinical guidelines of the Ministry of Health of the Russian Federation of the Russian Association of Endocrinologists “Algorithms for specialized medical care for patients with diabetes mellitus” (2019), an additional diagnostic indicator is the average daily plasma glucose level (AGG) for the last three months and its correlation with the level of HbA1c.

What can influence the result?

Patients with abnormal hemoglobin, such as those with sickle cells, will have low glycated hemoglobin. In addition, if a person suffers from anemia, severe bleeding, his test results may also be underestimated. On the contrary, A1c values ​​are overestimated with iron deficiency and with a recent blood transfusion (since liquid blood preservatives contain a high concentration of glucose).

Important Notes

The A1c test does not reflect sudden changes in blood glucose. Glucose fluctuations in patients with labile diabetes will also not be detected by this test.

Also recommended

• Plasma glucose
• Glucose tolerance test
• Fructosamine

Who orders the examination?

Therapist, endocrinologist.

Glycosylated hemoglobin – what is it, the norm in women and men

Published: 04/16/2012 Updated: 06/26/2023 Views: 324474

It is very important in the management of patients with diabetes to achieve optimal blood glucose levels. The patient can control the level of glucose in the blood independently (with portable glucometers) or in the laboratory.

The result of a single determination of glucose in the blood shows the concentration of glucose at the time of taking, therefore, it is not possible to make any assumptions about the state of the patient’s carbohydrate metabolism between measurements. It is possible to assess the patient’s carbohydrate metabolism over a long period of time only by measuring the concentration of glycosylated hemoglobin in the blood, according to the recommendations of the Committee for the Control of Diabetes and its Clinical Complications (DCCT).

According to DCCT studies, it has been shown that the risk of development and progression of long-term complications of type 1 diabetes is closely related to the degree of effectiveness of glycemic control, expressed in the content of glycated hemoglobin in the blood [10]. Specialists from the UK have shown that a decrease in the patient’s blood glucose, assessed by the concentration of HbA1c, reduces the incidence of microangiopathies in type 2 diabetes mellitus [4].

Characteristics of indicator

Glycosylated hemoglobin (the term “glycated hemoglobin” is also used) is formed as a result of non-enzymatic addition of glucose to the N-terminal regions of the β-chains of hemoglobin A1 _{globin and is designated as HbA1c. The concentration of HbA1c is directly proportional to the average concentration of glucose in the blood. In healthy people, the concentration of HbA1c in the blood is from 4.80 to 5.90%, in patients with diabetes its level is 2-3 times higher (depending on the degree of hyperglycemia).}

The resulting HbA1 accumulates inside the erythrocytes and persists throughout the life of the erythrocyte. The half-life of erythrocyte circulation in the bloodstream is 60 days, thus, the HbA1c concentration reflects the patient’s glycemia level 60-90 days before the study [2, 3].

A huge number of studies using traditional methods for measuring glucose content have confirmed the relationship between HbA1c and the level of glycemia of the patient [12-14]. Results of studies conducted by DCCT in 90s, served as the basis for confirming the hypothesis that the level of HbA1c reflects the level of glucose in the blood and is an effective criterion for monitoring patients with diabetes mellitus.

Standardization of methods for the study of glycosylated hemoglobin

In the early 90s, there was no interlaboratory standardization of methods for measuring glycosylated hemoglobin, which reduced the clinical effectiveness of this test [15-17]. In this regard, the American Association of Clinical Chemistry in 1993 formed a subcommittee on the standardization of methods for measuring glycated hemoglobin. As a result of his work, the National Glycosylated Hemoglobin Standardization Program (NGSP) was developed. Manufacturers of test systems for measuring glycated hemoglobin have been required to undergo rigorous testing to ensure that the results correspond to data obtained by reference DCCT methods. In case of a positive result of the check, the manufacturer is issued a “DCCT certificate of conformity”. The American Diabetes Association recommends that all laboratories use only NGSP-certified tests [7].

There are currently many methods for studying glycosylated hemoglobin:

• liquid chromatography;
• affinity chromatography;
• electrophoresis;
• column methods;
• immunological methods.

When a laboratory chooses an analyzer for glycated hemoglobin testing, preference should be given to analyzers based on the DCCT reference method, which is liquid chromatography. The use of standardized test methods enables the laboratory to obtain results that can be compared with data obtained using reference methods and published by DCCT. Such a comparison maximizes the reliability of the research results.

It is extremely important that the attending physician use in his work the results of studies obtained only in those laboratories that conduct the study of glycosylated hemoglobin using NGSP certified methods.

Study of HbA1c concentration in the laboratories of the Citylab Association

The concentration of glycosylated hemoglobin (HbA1c) in the laboratories of the Citilab Association is determined by the reference method (DCCT) of high performance liquid chromatography (HPLC), (the method is certified by NGSP), on D 10 analyzers from Bio-Rad, which is the world leader in the manufacture of glycosylated hemoglobin analyzers. This study is 23-10-002 – Glycosylated hemoglobin.

Mean blood glucose assessment

The DCCT study group demonstrated the clinical relevance of HbA1c as an estimate of mean blood glucose concentration (over 60-90 days). In these studies, patients had their daily glucose profile recorded every 3 months (seven measurements daily). The resulting profile was compared with the level of HbA1c. Over 36,000 studies have been conducted over 9 years. Empirically, a linear relationship between the average glucose content and the HbA1c level was obtained:

Average glucose concentration (mg / 100 ml) = 30. 9 x (HbA1c) -60.6, where:

HbA1c is the concentration of glycosylated hemoglobin.

Simply put, a 1% change in HbA1c corresponds to a 30 mg/100 ml (1.7 mmol/L) change in mean glucose.

Note: This relationship was obtained in the study of glucose concentration in capillary blood. The concentration of glucose in the blood serum is approximately 15% higher.

The diagram (Fig. 1) [11] can be used to interpret the results of HbA1c studies.

Rice. 1. Diagram of the control of carbohydrate metabolism in patients with diabetes mellitus

Note: The concentration of glucose is indicated in mmol / l, in brackets in mg / 100 ml, 1 – High risk of developing long-term complications such as retinopathy, nephropathy and neuropathy. 2 – Increased risk of hypoglycemic reactions in patients with type 1 or type 2 diabetes when taking insulin or oral hypoglycemic drugs.

To convert glucose concentration in mg/100 ml to SI units (mmol/l), the following formula is used:

Glucose (mg/100 ml) x 0. 0555 = Glucose (mmol/l)

Recommended testing frequency

The American Diabetes Association recommends that for patients whose therapy has been successful (stable carbohydrate metabolism), an HbA1c test should be performed at least 2 times a year, while in case of a change in diet or treatment, the frequency of testing should be increased to 4 times a year [7]. In the Russian Federation, according to the Targeted Federal Program “Diabetes Mellitus”, HbA1c testing should be carried out 4 times a year for any type of diabetes [1].

According to the American Diabetes Association, women with diabetes in the pre-pregnancy period need a special monitoring regimen. It is recommended to reduce the level of HbA1c in order to create optimal conditions in the body of the future mother for conception and fetal development. At the beginning, HbA1c should be tested monthly. When carbohydrate metabolism is stabilized with appropriate therapy, HbA1c testing should be performed at intervals of 6-8 weeks prior to conception [5, 6].

Modern studies have shown that many patients do not comply with the recommended interval between studies [8], however, experts have come to a common opinion that regular studies of HbA1c levels significantly reduce the risk of complications in patients with diabetes mellitus.

Interpretation of test results

The goal of hypoglycemic therapy in diabetes mellitus is to normalize blood glucose levels. DCCT studies have shown that intensive treatment prevents the patient from developing long-term complications such as retinopathy, nephropathy and neuropathy, or significantly delays their clinical manifestation. If patients strictly adhere to a regimen aimed at normalizing carbohydrate metabolism, the incidence of retinopathy decreases by 75%, nephropathy – by 35-36%, and the risk of polyneuropathy decreases by 60% [10].

Below are the therapeutic goals in the treatment of diabetes mellitus according to the Target Federal Program “Diabetes Mellitus”.

Table 1.

Therapeutic goals in the treatment of type 1 diabetes mellitus [1, 18]

Table 2.

Therapeutic goals in the treatment of type 2 diabetes mellitus [1, 19]

Note: In parentheses are glucose values ​​in mg/100 ml.

The Federal Target Program “Diabetes Mellitus” [1] adopted the values ​​recommended by the European Committee for Diabetes Recommendations [18, 19].

When evaluating the results of treatment in patients with concomitant diseases, young people, the elderly, pregnant women and patients with an unusual pattern of diabetes mellitus, other criteria for stabilizing carbohydrate metabolism should be used.

With an inadequate level of carbohydrate metabolism in a patient, additional measures are necessary, which depend on the clinical picture of the patient’s disease, such measures may include:

• enhanced patient education on self-monitoring of glucose levels;
• organization of patient support groups;
• regular examination by an endocrinologist;
• changes in drug therapy;
• more frequent testing of glucose and HbA1c.

Conclusions

1. The HbA1c study allows to assess the level of glycemia in a patient with diabetes mellitus 60-90 days prior to the study.
2. This study provides an opportunity to monitor the course of the disease and control the adequacy of the treatment.
3. An HbA1c study should be performed to assess the risk of complications in a patient with diabetes mellitus.

References

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