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Can dehydration cause low blood sugar: The request could not be satisfied


When Blood Sugar Is Too Low (for Kids)

Hypoglycemia (say: hi-po-gly-SEE-me-uh) is the medical word for low blood sugar level. It needs to be treated right away. Why? Because glucose, or sugar, is the body’s main fuel source. That means your body — including your brain — needs glucose to work properly.

When blood sugar levels go lower than they’re supposed to, you can get very sick. Your parents and your diabetes health care team will tell you what your blood sugar levels should be and what to do if they get too low.

The Causes of Low Blood Sugar

Low blood sugar levels can happen to kids with diabetes because of the medicines they have to take. Kids with diabetes may need a hormone called insulin and/or diabetes pills to help their bodies use the sugar in their blood. These medicines help take the sugar out of the blood and get it into the body’s cells, which makes the level of sugar in the blood go down.

But sometimes it’s a tricky balancing act, and blood sugar levels can get too low. Kids with diabetes need to keep their blood sugar levels from getting too high or too low. How do they do it? With help from grown-ups, they keep three things in balance:

Each one of these can affect the other. For instance, eating more might mean a kid needs more insulin. And exercising might create the need for an extra snack. Again, a grown-up can help you learn how to juggle those three activities so you keep feeling good.

Some things that can make low blood sugar levels more likely to happen are:

  • skipping meals and snacks
  • not eating enough food at a meal or snack
  • exercising longer or harder than usual without eating something extra
  • getting too much insulin
  • not timing the insulin doses properly with meals, snacks, and exercise
  • taking a long bath or shower right after an insulin shot

Signs That Blood Sugar Levels Are Low

There are a bunch of symptoms that someone with low blood sugar might have. It’s not the same for everybody. The symptoms are as minor as feeling hungry and as serious as having seizures or passing out. Have you ever had low blood sugar? If so, do you remember how it felt? Noticing those problems early can help you if it happens again.

If you have diabetes and you have low blood sugar, you may:

  • feel hungry or have “hunger pains” in your stomach
  • feel shaky or like you’re trembling
  • have a rapid heart rate
  • feel sweaty or have cold, clammy skin
  • have pale, gray skin color
  • have a headache
  • feel moody or cranky
  • feel sleepy
  • feel weak
  • feel dizzy
  • be unsteady or stagger when walking
  • have blurred or double vision
  • feel confused
  • have seizures
  • pass out

If you think your blood sugar level could be low, tell a parent, teacher, or whoever is taking care of you. An adult can help you test your blood and get you treatment so you start feeling better.

How Are Low Blood Sugar Levels Treated?

When blood sugar levels are low, the goal is to get them back up quickly. Most kids who have low blood sugar need to:

  • eat, drink, or take something that contains sugar that can get into the blood quickly. Your mom or dad may give you really sugary foods or drinks, like regular soda, orange juice, cake frosting, glucose tablets, or glucose gel (a tube of sugary gel)
  • wait about 10 minutes to let the sugar work
  • recheck their blood sugar levels with a blood glucose meter to see if the levels are back to normal

Sometimes, blood sugar levels can get very low and you might not feel well enough or be awake enough to eat or drink something sugary. When this happens, kids need to get a glucagon shot. Glucagon (say: GLOO-kuh-gon) is a hormone that helps get your blood sugar level back to normal very quickly. Your doctor and diabetes health care team can tell you if you need to keep these shots on hand and will help you and your parents understand when it’s necessary to use one.

Your parents and other grown-ups who take care of you should know how to give glucagon shots. If you don’t have a glucagon shot — or the person you’re with doesn’t know how to use one — someone should call 911.


Can You Prevent Low Blood Sugar?

Hypoglycemia might sound a little scary, so you might wonder if you can avoid it. No matter how well they take care of themselves, kids with diabetes will sometimes have low blood sugar levels. But taking these steps can help:

  • Try to eat all your meals and snacks on time and don’t skip any.
  • Take the right amount of insulin.
  • If you exercise longer or harder than usual, have an extra snack.
  • Don’t take a hot bath or shower right after an insulin shot.
  • Stick to your diabetes management plan.

What else can you do? Wear a medical identification bracelet or necklace that says you have diabetes. Then, if you are not feeling well, whoever’s helping you — even if the person doesn’t know you — will know to call for medical help. Medical identification also can include your doctor’s phone number or a parent’s phone number. The quicker you get help, the quicker you’ll be feeling better.

Diabetes Insipidus | NIDDK

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What is diabetes insipidus?

Diabetes insipidus is a rare disorder that causes the body to make too much urine. While most people make 1 to 3 quarts of urine a day, people with diabetes insipidus can make up to 20 quarts of urine a day. People with this disorder need to urinate frequently, called polyuria. They may also feel thirsty all the time and drink lots of liquids, a condition called polydipsia.

Are diabetes insipidus and diabetes mellitus the same?

Diabetes insipidus is not the same as diabetes mellitus. Although both conditions can increase thirst, intake of liquids, and urination, they are not related.

  • In diabetes mellitus, the level of glucose in your blood, also called blood sugar, is too high. Your kidneys try to remove the extra glucose by passing it in your urine.
  • In diabetes insipidus, your blood glucose levels are normal, but your kidneys can’t properly concentrate urine.

How common is diabetes insipidus?

Diabetes insipidus is rare, affecting about 1 in 25,000 people worldwide.1

Who is more likely to have diabetes insipidus?

People of all ages can develop diabetes insipidus. You are more likely to develop the condition if you1,2

  • have a family history of diabetes insipidus
  • had brain surgery or a major head injury
  • take medicines that can cause kidney problems, including some bipolar disorder medicines and diuretics
  • have metabolic disorders (high blood calcium or low blood potassium levels)

What are the complications of diabetes insipidus?

The main complication of diabetes insipidus is dehydration, which happens when your body loses too much fluid and electrolytes to work properly. If you have diabetes insipidus, you can usually make up for the large amount of fluids you pass in your urine by drinking more liquids. But if you don’t, you could quickly become dehydrated.

Symptoms of dehydration may include

  • thirst
  • dry mouth
  • feeling dizzy or light-headed when standing
  • feeling tired
  • difficulty performing simple mental tasks
  • nausea
  • fainting

Seek care right away

Severe dehydration can lead to seizures, permanent brain damage, and even death. Seek care right away if you feel

What are the symptoms of diabetes insipidus?

The main symptoms of diabetes insipidus are

  • needing to urinate often, both day and night
  • passing large amounts of light-colored urine each time you urinate
  • feeling very thirsty and drinking liquids very often

People with diabetes insipidus often feel thirsty all the time and drink lots of liquids.

What causes diabetes insipidus?

Diabetes insipidus is usually caused by problems with a hormone called vasopressin that helps your kidneys balance the amount of fluid in your body. Problems with a part of your brain that controls thirst can also cause diabetes insipidus. Specific causes vary among the four types of diabetes insipidus: central, nephrogenic, dipsogenic, and gestational.2

Central diabetes insipidus

In central diabetes insipidus, your body doesn’t make enough vasopressin, also called “antidiuretic hormone.” Vasopressin is produced in your hypothalamus, a small area of your brain near the pituitary gland. When the amount of fluids in your body falls too low, the pituitary gland releases vasopressin into your bloodstream. The hormone signals your kidneys to conserve fluids by pulling fluids from your urine and returning fluid to your bloodstream. But if your body can’t make enough vasopressin, the fluid may get flushed out in your urine instead.

Causes of central diabetes insipidus include

Nephrogenic diabetes insipidus

In nephrogenic diabetes insipidus, your body makes enough vasopressin but your kidneys don’t respond to the hormone as they should. As a result, too much fluid gets flushed out in your urine. Causes include

Dipsogenic diabetes insipidus

In this type of diabetes insipidus, a problem with your hypothalamus causes you to feel thirsty and drink more liquids. As a result, you may need to urinate often. Causes include

  • damage to your hypothalamus from surgery, infection, inflammation, a tumor, or a head injury
  • some medicines or mental health problems

Gestational diabetes insipidus

Gestational diabetes insipidus is a rare, temporary condition that can develop during pregnancy. This type of diabetes insipidus occurs when the mother’s placenta makes too much of an enzyme that breaks down her vasopressin. Women who are pregnant with more than one baby are more likely to develop the condition because they have more placental tissue. 3 Because the liver plays a role in curbing the enzyme that breaks down vasopressin, diseases and conditions that affect liver function also increase risk. Examples include preeclampsia and HELLP syndrome.

How do health care professionals diagnose diabetes insipidus?

Your health care professional will do a physical exam and ask questions about your health history, including your family’s health. Other tests and procedures may include

  • Urinalysis. A urinalysis can show if your urine is too diluted, or watery. It can also show if the level of glucose in your blood is too high, which is caused by diabetes mellitus, not diabetes insipidus.
  • Blood tests. A blood test can measure sodium levels and the amount of certain substances in your blood, which can help diagnose diabetes insipidus and, in some cases, determine the type.
  • Water deprivation test. This test can help health care professionals diagnose diabetes insipidus and identify its cause. The test involves not drinking any liquids for several hours. A health care professional will measure how much urine you pass, check your weight, and monitor changes in your blood and urine. In some cases, the health care professional may give you a man-made version of vasopressin or other medicines during the test.
  • Magnetic resonance imaging (MRI). An MRI uses magnets and radio waves to make pictures of your brain tissues. Your health care professional may order this test to look for damage to your hypothalamus or pituitary gland that could cause diabetes insipidus.
  • Stimulation tests. During these tests, you are given an intravenous solution that stimulates your body to produce vasopressin.4,5 A health care professional then measures your blood level of copeptin, a substance that increases when vasopressin does. Results can indicate if you have diabetes insipidus or a different condition called primary polydipsia, which can cause you to drink lots of liquids.

How do health care professionals treat diabetes insipidus?

The main way to treat diabetes insipidus is to drink enough liquids to prevent dehydration. But doing so can disrupt your regular lifestyle, including your sleep. Your health care professional may refer you to a specialist, such as a nephrologist or an endocrinologist for more specific treatments. Other treatments vary by cause.

Central diabetes insipidus

Health care professionals most often treat central diabetes insipidus with a man-made hormone called desmopressin, which replaces the vasopressin your body is not making.2,6 You can take this medicine as a nasal spray, a pill, or a shot.

Nephrogenic diabetes insipidus

In some cases, nephrogenic diabetes insipidus may go away after treating its cause. For example, switching medicines or taking steps to balance the amount of calcium or potassium in your body may be enough to resolve the problem. Your health care professional may also prescribe a class of diuretic medicines called thiazides to help reduce the amount of urine your kidneys make. 2,7 Other treatments can include nonsteroidal anti-inflammatory drugs or other types of diuretics.

Dipsogenic diabetes insipidus

Researchers haven’t found an effective way to treat dipsogenic diabetes insipidus. Sucking on ice chips or sugar free candies to moisten your mouth and increase saliva flow may help reduce your thirst. If you wake up many times at night to urinate, your health care professional may suggest you take a small dose of desmopressin at bedtime. Your health care professional may also monitor your blood levels of sodium, which can drop too low if you have this condition.

Gestational diabetes insipidus

Health care professionals treat gestational diabetes insipidus with desmopressin, which is safe for both mother and baby. An expectant mother’s placenta does not destroy desmopressin as it does vasopressin. Gestational diabetes insipidus usually goes away after the baby is born, but may return if the mother becomes pregnant again.

Most people with diabetes insipidus can prevent serious problems and live a normal life if they follow their health care professional’s recommendations and keep their symptoms under control.

How do eating, diet, and nutrition affect diabetes insipidus?

Researchers have not found that eating, diet, and nutrition play a role in causing or preventing diabetes insipidus. To reduce symptoms, your health care professional may suggest you eat a diet that is low in salt and protein to help your kidneys make less urine. In some cases, these changes alone may be enough to keep your symptoms under control, particularly if you have nephrogenic diabetes insipidus.2,7

Clinical Trials for Diabetes Insipidus

The NIDDK conducts and supports clinical trials in many diseases and conditions, including kidney diseases. The trials look to find new ways to prevent, detect, or treat disease and improve quality of life.

What are clinical trials for diabetes insipidus?

Clinical trials—and other types of clinical studies—are part of medical research and involve people like you. When you volunteer to take part in a clinical study, you help doctors and researchers learn more about disease and improve health care for people in the future.

Find out if clinical studies are right for you.

Watch a video of NIDDK Director Dr. Griffin P. Rodgers explaining the importance of participating in clinical trials.

What clinical studies for diabetes insipidus are looking for participants?

You can view a filtered list of clinical studies on diabetes insipidus that are open and recruiting at www.ClinicalTrials.gov. You can expand or narrow the list to include clinical studies from industry, universities, and individuals; however, the National Institutes of Health does not review these studies and cannot ensure they are safe. Always talk with your health care provider before you participate in a clinical study.


[1] Levy M, Prentice M, Wass J. Diabetes insipidus. British Medical Journal. 2019;364. doi: 10.1136/bmj.l321

[2] Christ-Crain M, Bichet DG, Fenske WK, et al. Diabetes insipidus. Nature Reviews. Disease Primers. 2019;5(1):54. doi: 10.1038/s41572-019-0103-2

[3] Quigley J, Shelton C, Issa B, Sripada S. Diabetes insipidus in pregnancy. The Obstetrician & Gynaecologist. 2018;20(1):41–48. doi: 10.1111/tog.12450

[4] Fenske W, Refardt J, Chifu I, et al. A copeptin-based approach in the diagnosis of diabetes insipidus. New England Journal of Medicine. 2018;379(5):428–439. doi: 10.1056/NEJMoa1803760

[5] Winzeler B, Cesana-Nigro N, Refardt J, et al. Arginine-stimulated copeptin measurements in the differential diagnosis of diabetes insipidus: a prospective diagnostic study. Lancet. 2019;394(10198):587–595. doi: 10.1016/S0140-6736(19)31255-3

[6] Baldeweg SE, Ball S, Brooke A, et al. Society for Endocrinology clinical guidance: inpatient management of cranial diabetes insipidus. Endocrine Connections. 2018;7(7):G8–G11. doi: 10.1530/EC-18-0154

[7] Kavanagh C, Uy NS. Nephrogenic diabetes insipidus. Pediatric Clinics of North America. 2019;66(1):227–234. doi: 10.1016/j.pcl.2018.09.006

Hyperosmolar Hyperglycemic Syndrome


What is hyperosmolar hyperglycemic syndrome (HHS)?

Hyperosmolar hyperglycemic syndrome (HHS) is a serious complication of diabetes mellitus. HHS occurs when a person’s blood glucose (sugar) levels are too high for a long period, leading to severe dehydration (extreme thirst) and confusion.

Hyperosmolar hyperglycemic syndrome is also known by many other names, including:

  • Diabetic HHS.
  • Diabetic hyperosmolar syndrome.
  • Hyperglycemic hyperosmolar nonketotic coma (HHNK).
  • Hyperosmolar coma.
  • Hyperosmolar hyperglycemic nonketotic syndrome (HHNS).
  • Hyperosmolar hyperglycemic state.
  • Nonketotic hyperosmolar syndrome (NKHS).

Who is affected by hyperosmolar hyperglycemic syndrome (HHS)?

HHS most often affects people who have type 2 diabetes who are:

  • Older (usually in their 60s or 70s).
  • African-American, Native American or Hispanic.
  • Affected by other health issues, such as infection, illness or heart conditions.

HHS can be fatal if it’s not treated. Rarely, HHS can affect children and young adults who have type 1 or type 2 diabetes, especially if they are obese. Very rarely, people who have not yet been diagnosed with diabetes can develop HHS.

How common is hyperosmolar hyperglycemic syndrome (HHS)?

HHS is less common than other major complications associated with diabetes. HHS accounts for less than 1% of hospital admissions for people with diabetes.

Symptoms and Causes

What causes hyperosmolar hyperglycemic syndrome (HHS)?

People who have diabetes have too much glucose (sugar) in their blood. The glucose builds up because their bodies either don’t make enough insulin, or have trouble using the insulin that they do make. (Insulin is a naturally occurring hormone, produced by the beta cells of the pancreas, which helps the body use sugar for energy.)

HHS occurs when the blood sugar of a person with diabetes becomes too high (hyperglycemia) for a long time. The extra sugar is passed into the urine, which causes the person to urinate frequently. As a result, he or she loses a lot of fluid, which can lead to severe dehydration (extreme thirst).

HHS usually develops in people who do not have their type 2 diabetes under control and they:

  • Have an illness or infection, such as pneumonia or a urinary tract infection.
  • Stop taking medication to manage their diabetes.
  • Have a heart attack or stroke.
  • Take certain medications—such as steroids or diuretics—that can cause the syndrome.

What are the symptoms of hyperosmolar hyperglycemic syndrome (HHS)?

Symptoms of HHS usually come on slowly, and can take days or weeks to develop. Symptoms include:

  • High blood sugar level (over 600 mg/dL).
  • Confusion, hallucinations, drowsiness or passing out.
  • Dry mouth and extreme thirst that may eventually get better.
  • Frequent urination.
  • Fever over 100.4 degrees Fahrenheit.
  • Blurred vision or loss of vision.
  • Weakness or paralysis that may be worse on one side of the body.

Diagnosis and Tests

How is hyperosmolar hyperglycemic syndrome (HHS) diagnosed?

You should seek medical attention right away if you are diabetic and you have these symptoms:

  • Extreme thirst.
  • Frequent urination.
  • Confusion, or a change in your mental state.
  • Changes in your vision.

Your doctor will examine you, ask about your symptoms, and order a blood test to check your blood sugar level. A very high blood sugar level (over 600 mg/dL) with low ketone levels (acids in blood and urine) will help the doctor make a diagnosis of HHS.

Management and Treatment

How is hyperosmolar hyperglycemic syndrome (HHS) treated?

To treat HHS, your doctor will give you intravenous (IV) medications. These include:

  • Fluids to hydrate you.
  • Electrolytes (such as potassium) to balance the minerals in your body.
  • Insulin to control your blood sugar levels.

Your doctor will also treat any underlying conditions or infections that may have caused the HHS. You will usually stay in the hospital so that your healthcare team can watch you closely for any complications.

What are the side effects of the treatment for hyperosmolar hyperglycemic syndrome (HHS)?

The IV electrolytes or fluids used to treat dehydration do not have side effects. Side effects from insulin include:

Your doctor will treat you for hypoglycemia if your blood sugar gets too low while you are in the hospital.

What are the complications associated with hyperosmolar hyperglycemic syndrome (HHS)?

HHS is a very serious medical condition. If it is not treated, it can lead to:

  • Seizures.
  • Coma.
  • Swelling of the brain.
  • Organ failure.
  • Death.

What can I do to relieve symptoms of hyperosmolar hyperglycemic syndrome (HHS)?

If you have symptoms of HHS, you should drink plenty of water and call 911 or go to the emergency room immediately. You will receive an IV with fluids and insulin to relieve your symptoms.


Can hyperosmolar hyperglycemic syndrome (HHS) be prevented?

The best way to prevent HHS is by following a healthy lifestyle and managing your diabetes. You should:

  • Check your blood sugar frequently to make sure you’re staying within your target range.
  • Take your insulin and other diabetes medications as directed by your doctor.
  • Follow a healthy diet.
  • Never drink alcohol on an empty stomach.
  • Get more rest and check your blood sugar more often when you are sick.
  • Know the symptoms of HHS and get help right away if you have any of them.

Outlook / Prognosis

What is the prognosis (outlook) for patients who have hyperosmolar hyperglycemic syndrome (HHS)?

The outlook for patients who have HHS largely depends on the person’s age, general health and how severe the disease is. Up to 20% of people who have HHS die from the condition.

If you’ve had HHS, you will need to work closely with your doctor once you are home from the hospital. You can reduce your risk of developing HHS again by controlling your diabetes and managing your diet and lifestyle.

Living With

When should I call my doctor about hyperosmolar hyperglycemic syndrome (HHS)?

HHS is a serious medical condition. If you are diabetic, you should call 911 or seek emergency medical help if you:

  • Ever have a blood sugar level over 400 mg/dL.
  • Are confused or disoriented.
  • Feel thirstier than usual.
  • Have to urinate more often than usual.
  • Have changes in your vision.
  • Feel weak or paralyzed anywhere in your body.

Dehydration & Hyperglycemia | Study.com


Dehydration is a condition in which the body shows symptoms of severely low fluid content. Low water intake is the most obvious cause of dehydration. But it can also have many other reasons, like underlying health conditions, exercise, and environmental factors. Dehydration can be treated with oral or injection fluids supply, depending on the severity of patients condition.

Relationship between dehydration and hyperglycemia

Dehydration in people with hypoglycemia deserves special attention, because it is one of the symptoms of hyperglycemia. As a reaction to over-saturated blood with glucose, our body requires more fluids to balance out the concentration and to flush out the excess glucose. That is why hyperglycemia often goes hand-in-hand with thirst. If severe dehydration occurs in people with hyperglycemia, a life threatening condition called hyperosmolar hyperglycemic state (HHS) can occur. This condition is a result of dehydration caused by hypoglycemia and causes a coma that can lead to death if not treated in time.

Dehydration in hypoglycemia also works the other way around. If a person is severely dehydrated, then the concentration of elements in blood, among which also glucose, is high in relation to the available amount of fluids. If we measure blood glucose in dehydrated people with diabetes, we see hyperglycemia values. Besides that, symptoms of dehydration like thirst, fatigue, blurred vision and headache are also the symptoms that characterize hyperglycemia. People with hyperglycemia and diabetes are therefore advised to keep their liquid intake optimal, especially when feeling typical symptoms, to avoid glucose peaks in blood and further complications.

Low concentration solution

Kidney function

Because kidneys play an important role in management of fluids in the body, severe and persistent dehydration might also be a sign of their dysfunction. All people that experience long-term thirst and feel dehydrated should take note of this and contact doctor. But for people with hyperglycemia and diabetes it is especially important to take further action. Dehydration in hyperglycemia patients would have very dangerous consequences for kidneys. Because kidney failure is a common diabetes complication already, in combination with bad fluid balance it can become very dangerous.

Lesson Summary

Hyperglycemia and dehydration can be standing alone health conditions that have specific symptoms and treatment methods. But dehydration in hyperglycemia patients requires special attention because specifically for them dehydration can be an urging sign of worsening condition. Dehydration can be both, a symptom and a cause of hyperglycemia. Therefore monitoring fluid intake and taking note of thirst signals is very important for hyperglycemia patients in order to avoid complications. On the other hand, sufficient hydration could also help to prevent peaks of high blood glucose.

Effect of dehydration on blood tests – Ashraf – 2017 – Practical Diabetes

In this third article in our ‘Test tips’ series, Dr Muhammad Masood Ashraf and Dr Rustam Rea examine the effects of dehydration on all essential diabetes blood tests, and provide guidance on key practical points to consider.


Dehydration is common in patients presenting to the acute admissions ward. The most common reasons include poor oral intake and fluid loss from:

  • Gastrointestinal tract (e.g. diarrhoea, vomiting).
  • Skin (e.g. fever, burns).
  • Urine (e.g. glucosuria, diuretic therapy, diabetes insipidus, diabetic ketoacidosis).

A reduction of the central circulating blood volume due to hypovolaemia accompanying dehydration results in a fall in cardiac filling pressure and stroke volume and, if uncompensated, a fall in cardiac output. The body can compensate by moving water from the extravascular to the intravascular space.1, 2 As a result of these fluid shifts, changes in electrolytes and water concentrations in various body compartments occur which are reflected in many blood tests results. This is classically seen in patients with diabetic ketoacidosis and Hyperglycaemic Hyperosmolar State (previously HONK).

The clinical and biochemical features of dehydration3 are summarised in Box 1.

Box 1. Summary of the clinical and biochemical features of dehydration

Clinical features of dehydration

  • Dry mucus membrane
  • Dry skin
  • Reduced skin turgor
  • Reduced axillary sweating
  • Orthostatic hypotension
  • Tachycardia and hypotension (indicates shock)
  • Cognitive impairment
  • Reduced urinary output (<0.5 ml/kg/h is suggestive of acute kidney injury)
  • Concentrated urine and high osmolality

Biochemical changes

  • Raised serum urea
  • Raised creatinine
  • Reduced estimated glomerular filtration rate (eGFR)
  • Increased urea:creatinine ratio
  • Hypernatraemia (loss of water greater than salt loss)
  • Raised serum or urine osmolality
  • Raised urine specific gravity

Effect of dehydration on haemoglobin, haematocrit and HbA


Both haemoglobin and haematocrit increase in a dehydrated person.2, 4 Hiroshi Nose1 and colleagues induced dehydration in 10 subjects by exercise and checked haemoglobin (Hb), haematocrit (Hct), Na, K+, Cl, and plasma osmolality at 0 minutes, 30 minutes and 60 minutes after exercise. Figure 1 shows the change in Hct, Hb, and plasma solids before and after dehydration. Immediately after exercise, these increased from 42.7 ± 0.5% to 44.7 ± 0.5%, 14.8 ± 0.2 g/dl to 15.8 ± 0.2 g/dl, and 8.4 ± 0.1 g/dl to 9.1 ± 0.1 g/dl, respectively. The significant differences observed before and after dehydration were maintained for the next 60 minutes.


A 75-year-old lady was admitted with history of cough, high-grade fever and reduced oral intake for four days. She also complained of reduced urine output. Her past medical history included type 2 diabetes, hypertension, migraine, gastro-oesophageal reflux disease, and a non-functioning pituitary microadenoma. Her regular medication included hydrochlorothiazide, amlodipine, metformin and omeprazole. She was found to have dry mucous membranes, temperature 38.2 °C, and BP 90/60 mmHg. Chest examination revealed L-sided basal crackles.

Her blood tests on admission and after starting IV fluid replacement are summarised in the Table below.

Tests 9 March 11 March 13 March
Hb (g/L) 135 111 113
WBC 24.2 × 109 16.9 × 109 12 × 109
Haematocrit 0.443 0.368 0.369
MCV 96.9 96.1 94.4
Na+ (mmol/L) 160 156 150
K (mmol/L) 4.4 3.4 3.4
Urea (mmol/L) 31.3 18.9 9.9
Creatinine (µmol/L) 263 145 133
Glucose (mmol/L) 19 11 9
HbA1c (mmol/mol) 75
Total proteins (g/L) 60 48
Albumin (g/L) 29 23
ALT (IU/L) 24 23
ALP (IU/L) 132 126
Total bilirubin (µmol/L) 8 10
Total globulin (g/L) 31 28

The effect of dehydration on blood tests, highlighted in darker blue tint in the above Table, indicates that haemoglobin, haematocrit, urea/creatinine, Na+/K+, glucose and protein levels change significantly with improvement in the hydration status of the patient.

A number of questions arise from these data, and these are:

  • Is the poor glycaemic control a marker of dehydration or uncontrolled diabetes?
  • Is the drop in haemoglobin due to blood loss?
  • Do the renal function tests suggest dehydration as a primary cause of acute kidney injury?
  • Does the drop in albumin indicate deterioration in the liver’s synthetic function?

Haematocrit (Hct), haemoglobin (Hb) concentration, and plasma (Pl) solids are shown as means ± SE of 10 subjects before (C) and at 0, 30, and 60 minutes after dehydration. Significant differences were observed for all variables between control and dehydrated conditions (0, 30, and 60 minutes). There were significant differences between 0 minutes and the other 2 dehydrated conditions (30 and 60 minutes)

HbA1c is the measure of glycaemic status of an individual over the last three months.5 It is formed by a non-enzymatic reaction which occurs between glucose and the N-end of the beta chain.5 There is very little literature available on data search to suggest that dehydration directly affects HbA1c. However, a rise in urea level as a result of dehydration can alter the HbA1c test results depending on the assay.6

One study showed that in patients with uraemia, HbA1c measured by ion exchange chromatography was significantly elevated, but this was not correlated with the degree of glucose intolerance.7 This was due to the excessive amount of cyanate derived from the urea, which causes carbamylation at the N-terminal valine residue. This carbamylated haemoglobin (carbHb) results in an increase in the HbA1 (a + b) and, hence, the increased levels of HbA1.6, 8 However, newer ion-exchange HPLC assay methods show improved separation of the HbA1c fraction from other haemoglobin fractions and therefore no interference from carbHb.9

Effect of dehydration on CBG measurements

Hypotension as a result of dehydration results in decrease in perfusion and increase in glucose utilisation in the local tissue leading to false low results of capillary blood glucose (CBG) tests. One study assessed the validity of the CBG measurements in the hypotensive, critically-ill patients. Capillary glucose values were significantly lower than those obtained from testing venous blood on the reagent strips and also lower than laboratory glucose measurements. Capillary glucose values in the hypotensive group were 33% lower than venous laboratory glucose values, and were significantly lower than the values obtained in the normotensive group.10

Effect of dehydration on blood glucose

One study has looked at the effect of dehydration in frogs and demonstrated that dehydration can increase blood glucose levels.11 The rise in glucose was found to be out of proportion to changes in metabolite concentrations that could be due to passive concentration of the plasma (haemoconcentration) as a result of dehydration. Glucose was significantly elevated even in 12.2% of dehydrated frogs and rose progressively to a final level 23.6 times higher than controls in 50% of dehydrated frogs.

Another study showed an increase in hepatic glucose production, with increased plasma glucose levels during hyperosmolality which can be caused by dehydration.12 The very high levels of venous glucose seen in patients with Hyperglycaemic Hyperosmolar State often resolve rapidly with rehydration alone without the need for insulin. This would suggest a significant effect of dehydration on venous glucose concentration.

Effect of dehydration on renal function tests

Dehydration has multiple effects on the kidney. The loss of body water leads to an increase in serum osmolality and activation of vasopressin which results in urinary concentration.13 This can be seen clearly in the above given Vignette.

Nose1 and colleagues also demonstrated sustained effects on plasma electrolyte concentration before and after dehydration (Figure 2).

Changes in electrolyte concentrations and osmolality (Posmol) in plasma after dehydration. Significant differences were observed for all variables between control (C) and dehydrated conditions (0, 30, and 60 minutes)

However, there is an exception in the case of patients with cranial diabetes insipidus (CDI).

Dehydrated patients usually present with an elevated serum urea level, owing in part to increased renal reabsorption of urea mediated by antidiuretic hormone (ADH). Serum urea values fall in patients with ADH deficiency (CDI) and this fact can be used to distinguish patients dehydrated because of CDI from those with usual hypertonic dehydration and intact ADH secretion. In one study, the mean serum urea level was 2.9 mmol/L in the CDI group and 15.4 mmol/L in the patients without CDI, while the mean serum sodium level was 155 mmol/L in both groups.13

Effect of dehydration on lipid profile

The effect of dehydration on lipid profile has been investigated in fasting subjects.14 Subjects were fasted, initially with no fluid replacement and then with salt and water supplementation. Subjects who had fasted with no fluids had a higher total serum cholesterol, HDL cholesterol, LDL cholesterol, apolipoprotein A-1, and apolipoprotein B, compared to subjects who had fasted with prior fluid and salt replacement.

Effect of dehydration on liver function tests

The above given Vignette demonstrates a significant difference in serum total proteins and albumin levels in a dehydrated patient, before and after hydration with intravenous fluids. However, bilirubin and liver enzymes levels remained unchanged, indicating that changes in protein levels were essentially due to hydration status rather than liver abnormality per se.


Clinicians should take the hydration status of the patient into account before interpreting the laboratory results. Before routine blood tests, patients should avoid unnecessary physical activity, avoid hot dry environments, ensure adequate intake of water, and avoid diuretic substances such as caffeine.

Key points

  • HbA1c values can vary depending on the assay because of rise in urea level as a result of dehydration; however, there is no interference with modern assays
  • Capillary blood glucose values in a dehydrated person can be significantly lower than the values obtained by venous reagent strips or laboratory glucose measurements
  • Dehydration can increase the blood glucose levels per se
  • Dehydration leads to an increase in plasma osmolarity and urea levels, seen particularly in Hyperglycaemic Hyperosmolar State