Also called: Insulin Reaction


Hypoglycemia is abnormally low glucose (blood sugar). It can occur when a person’s levels of glucose and insulin are unbalanced.

Many people with diabetes refer to hypoglycemia as an “insulin reaction.” Insulin is a hormone necessary for moving glucose from the blood to the cells of the body. Without insulin, the glucose remains in the blood and the body does not receive fuel for energy.  

Mild cases of hypoglycemia can cause dizziness or weakness. Severe cases can lead to convulsions, brain damage or diabetic coma.

Low blood sugar can happen to anyone with diabetes, especially those who take insulin or other diabetes medication (antidiabetic agents). As with hyperglycemia (high blood sugar), people with diabetes can prevent hypoglycemia by following a physician-recommended diabetes management plan involving diet, exercise and medications.

Patients should determine what triggers their low blood glucose and, in consultation with their physician, adjust their diabetes management plan to remain as close as possible to their target glucose range. Despite these efforts, unexplained episodes of low blood glucose may occur.

It is essential for a person with diabetes to recognize the symptoms of hypoglycemia and know how to treat it. Patients can avoid the advanced symptoms and complications of hypoglycemia by frequently checking their glucose levels with a glucose meter and treating low glucose immediately.

A physician will recommend how often a patient should test and what the individual’s target glucose range should be. This range is usually based on factors such as age, the presence of diabetic complications or other medical conditions, and the patient’s tendency to have hypoglycemia unawareness – a condition in which the normal symptoms associated with hypoglycemia are not felt or noticed.

It is important to note that the treatment of hypoglycemia associated with diabetes is complex, and all recommendations for treatment must be made by the physician providing diabetic care.

About hypoglycemia

Hypoglycemia is abnormally low glucose (blood sugar). It can occur when a person’s levels of insulin and glucose are out of balance.

As with hyperglycemia (high blood glucose), low blood glucose can happen to anyone with diabetes. It occurs most often in people who use insulin. All patients with type 1 diabetes and some patients with type 2 diabetes use insulin. Those who take certain other diabetes medications (antidiabetic agents) are also at an increased risk.

When a person eats food, much of it is broken down into glucose, the form of sugar that is used to fuel the body. The glucose is passed into the bloodstream where it is used by cells for energy. For the glucose to reach the cells, the hormone insulin must be present.

Insulin is produced by beta cells in the pancreas, a glandular organ located behind the stomach. As the insulin enters the blood, it stimulates the receptors in muscle, fat and other cells to remove glucose from the bloodstream. Hypoglycemia occurs when the body’s glucose is used up too quickly, when glucose is released into the bloodstream too slowly or when too much insulin is released into the bloodstream.

The American Diabetes Association (ADA) has established guidelines for glucose goals for people with diabetes. The guidelines list normal blood glucose levels for whole blood and plasma. Different tests measure glucose in different ways. Most glucose meters measure the glucose level in a blood sample as whole blood (with all components intact). Most laboratory tests measure the glucose in plasma (the fluid portion of the blood that contains water, minerals and proteins). In addition, some glucose meters translate whole blood readings into plasma readings. Because plasma readings are higher than whole blood glucose measurements, it is important for patients to know whether their test results are presented as whole blood or plasma measurements.

The ADA’s guidelines for glucose goals for people with diabetes are:  

Time of DayWhole BloodPlasma
Before meals80 to 12090 to 130
1 to 2 hours after mealsLess than 170Less than 180
Bedtime100 to 140110 to 150

However, these ranges are not appropriate for everyone. Target blood glucose range is a personalized number given by a physician. It is usually based on factors such as age and presence of diabetic complications or other medical conditions. Hypoglycemia unawareness (a condition in which the normal symptoms associated with hypoglycemia are not felt or noticed) is also taken into consideration when determining the patient’s range.  People with diabetes should aim to keep their glucose levels within their personalized range by following their diabetes management plan.

The normal body can detect when it has enough insulin and will automatically stop releasing it. People with diabetes who take insulin or some other diabetes medications (antidiabetic agents) must calculate how much medicine they will need to counteract the effects of exercise and diet on their glucose levels. This is an important factor because the body’s mechanisms to regulate insulin release in individuals with diabetes are defective. Low glucose usually occurs just before meals, when insulin is peaking, or during and after exercise. Too little food or too much exercise in comparison to medication dosage may result in low glucose.

Low glucose is also common in the middle of the night. Nighttime hypoglycemia is dangerous because the patient may not be awake enough to feel the symptoms and could slip into a coma. Nighttime (nocturnal) hypoglycemia can be confirmed by testing blood glucose levels at 2 or 3 a.m. Patients may be encouraged to wake for such testing if they have any signs or symptoms of nighttime hypoglycemia. If there is evidence of nighttime hypoglycemia, the patient should immediately discuss it with the physician because changes in the diabetes management plan may be necessary.

Nocturnal hypoglycemia can cause rebound hyperglycemia the next morning. This is known as the Somogyi effect.

It is essential for people with diabetes to treat mild or moderate hypoglycemia quickly because it can rapidly develop into severe hypoglycemia, sometimes known as insulin shock. Severe hypoglycemia is the point at which people with diabetes are unable to treat their low blood glucose independently.

Low blood glucose first affects the autonomic nervous system. As glucose levels continue to drop, the brain begins to suffer from not receiving enough glucose, its major source of energy. Severe hypoglycemia can lead to seizures, unconsciousness, permanent brain damage and a potentially deadly diabetic coma.

The effects of low blood glucose on the autonomic nervous system and brain can increase a person’s risk of injuries from falls and motor vehicle accidents. It is advised that people with diabetes check their glucose level before driving, or engaging in other activities that require a high level of concentration, even if they do not suspect that it is low.

Patients should try to determine the cause of low glucose readings and report their findings to their physician. If low readings continue, a physician may make adjustments to the patient’s diabetes management plan, including changes in insulin dose, diet, or eating or exercise schedule. If poor control of glucose continues, other options may be available for such cases of unstable diabetes. 

Ketotic hypoglycemia is a rare childhood disorder combining ketosis (higher-than-normal levels of a waste product called ketones) and hypoglycemia. The condition is unrelated to diabetes.

Potential causes of hypoglycemia

Hypoglycemia occurs when levels of insulin and glucose (blood sugar) are out of balance. It occurs most often in patients who use insulin. All patients with type 1 diabetes, some people with type 2 diabetes and maturity-onset diabetes of the young (MODY), many people with latent autoimmune diabetes of adulthood (LADA) and most women with gestational diabetes use insulin.

Many factors can alter glucose levels in people with diabetes. Common triggers of low blood glucose in people with diabetes include:

  • Taking too much insulin or other diabetes drugs (antidiabetic agents). Insulin and antidiabetic agents are used to decrease the amount of glucose circulating in the blood. Taking too much of these medications can bring glucose levels lower than they should be.
  • Exercising excessively. Exercise lowers glucose levels by encouraging the transfer of glucose from the blood to the cells, where it is used for energy. Too much physical activity in comparison to the amount of food eaten, or medications taken, can result in hypoglycemia.
  • Eating too little food. Food provides the body with glucose and raises blood glucose levels. Eating insufficient food in comparison to the dose of insulin or antidiabetic agents taken can result in hypoglycemia.
  • Delaying or skipping a meal or snack. Delaying or skipping a scheduled meal while still taking the scheduled dose of insulin or antidiabetic agents can cause hypoglycemia.
  • Eating too few carbohydrates. The majority of glucose in the blood after a meal comes from the carbohydrates in food. Not ingesting enough carbohydrates can result in glucose levels that are too low.
  • Drinking alcohol, especially on an empty stomach. Normally, the liver changes stored carbohydrates (glycogen) into glucose when blood glucose levels begin to drop. It then releases the glucose into the blood to prevent or delay a low blood glucose reaction. However, when alcohol is in the body, the liver concentrates on clearing the alcohol from the blood instead of creating glucose.
  • Improperly handling a glucose meter. Recent research suggests that many patients using manually coded glucose meters often do so incorrectly and may experience insulin dosing errors and glycemic problems.
  • Taking non-diabetes medication. Some medications can lower glucose levels, including:
    • Aspirin or other salicylates
    • Acetaminophen (painkiller)
    • Sulfonamides (used to treat infections)
    • Quinine (used to treat malaria)
    • Pentamidine (used to treat pneumonia)
    • Haloperidol (used to treat nervous, mental and emotional conditions)
    • Anabolic steroids

Other medications, such as heart and blood pressure medications (antihypertensives, such as beta blockers) can cause hypoglycemia unawareness, a condition in which the normal symptoms of low blood glucose are not felt or noticed.

Other triggers of low glucose can include:

  • Certain other endocrine disorders, including hypothyroidism, adrenal insufficiency or hypopituitarism (underactive pituitary gland)
  • Insulinoma (a rare tumor of the pancreas that results in the secretion of an excess amount of insulin).
  • Other sources of hyperinsulinemia.
  • Rare tumors that consume excess glucose.
  • Liver disease.
  • Prenatal conditions. When the glucose level of a pregnant woman with diabetes is persistently high, the fetus’ pancreas produces extra insulin. As a result, the baby may have hypoglycemia at birth.
  • Ketotic hypoglycemia. 
  • An inherited metabolic disorder called SCADD (short-chain acyl-coenzyme A dehydrogenase deficiency)

Sometimes the cause of low glucose in people who do not have diabetes is unknown (idiopathic).

Signs and symptoms of hypoglycemia

Symptoms of hypoglycemia are different for everyone and may change over time. Low glucose (blood sugar) first affects the autonomic nervous system, causing early warning signs to occur. Common mild signs and symptoms include: 

  • Shakiness or tremors
  • Sweating
  • Hunger
  • Dizziness or light-headedness
  • Anxiety
  • Rapid heartbeat

Other mild signs and symptoms may include:

  • Chills and cold sweats
  • Clamminess
  • Pale skin color
  • Nervousness, impatience or irritability

As hypoglycemia goes untreated, the brain begins to suffer from lower glucose. Common signs and symptoms of moderate to severe low blood glucose include:

  • Headache
  • Difficulty paying attention
  • Confusion
  • Sudden moodiness or behavior changes such as crying, sadness or anger

Other signs and symptoms of moderate to severe low blood glucose include:

  • Stubbornness or combativeness
  • Sleepiness or drowsiness
  • Nausea
  • Cloudy or blurred vision
  • Tingling sensation or numbness in the lips or tongue
  • Clumsy or jerky movements
  • Lack of coordination
  • Convulsions
  • Fainting/loss of consciousness

People with diabetes should also be aware of the symptoms of nighttime hypoglycemia – low blood glucose in the middle of the night. These may include:

  • Sheets and pajamas damp from sweat.
  • Nightmares or restless sleep.
  • Waking up with a headache.
  • Rapid heartbeat.
  • Still feeling tired in the morning.
  • Unusually high glucose readings in the morning (rebound hyperglycemia, also known as the Somogyi effect). The body can try to counteract the low glucose by releasing hormones that raise blood glucose.

Some people do not feel or recognize the symptoms of low blood glucose. This problem is known as hypoglycemia unawareness. Patients may have hypoglycemia unawareness if their blood glucose level drops below 50 milligrams per deciliter (mg/dL) without any symptoms.

The more episodes of hypoglycemia that occur, the harder it is for the body to detect the next episode. The body becomes less sensitive to the symptoms over time, making it a dangerous condition. The emotional and physical symptoms (e.g., shakiness, dizziness, hunger) may begin to fade after five years with diabetes. After 20 or more years, it is not uncommon for these symptoms to become too subtle to feel or recognize.

However, the mental symptoms of low glucose (e.g., difficulty paying attention, lack of coordination) do not fade. Over time, these subtle symptoms may become a patient’s best signal of low glucose.

It is important for people with diabetes to check their glucose levels often and to treat low glucose even when they feel fine, as recommended by their physician. Left undetected and untreated, low glucose can lead to permanent brain damage or a potentially fatal diabetic coma.

Diagnosis methods for hypoglycemia

Hypoglycemia, or abnormally low glucose (blood sugar), occurs occasionally in almost all people with diabetes. To diagnose a hypoglycemic episode, people with diabetes can perform glucose monitoring. This self-testing of glucose levels usually involves pricking the finger or arm for a sample of blood and placing that sample on a test strip. The strip is then analyzed by a glucose meter. The meter digitally displays the glucose level as a number in milligrams per deciliter (mg/dL).

Physicians may use the term Whipple triad in diagnosing hypoglycemia. This refers to:

  • Hypoglycemic symptoms
  • Evidence of hypoglycemia from a glucose test (and sometimes also with a c-peptide test and a blood test of insulin)
  • Resolution of symptoms when the level of glucose in the bloodstream returns to normal

The oral glucose tolerance test (OGTT) has been used to diagnose hypoglycemia, most often of the type known as reactive hypoglycemia. However, this glucose test is not used often because the test itself can trigger hypoglycemic symptoms. Glucose monitoring probably remains the most reliable means for measuring day-to-day glucose control and diagnosing hypoglycemia.

For difficult-to-detect hypoglycemia, a physician may recommend that a diabetic patient wear a continuous glucose sensor for three days to record blood sugar levels automatically every 20 minutes. Later, the physician can analyze the data to determine if low glucose levels are occurring at particular times of the 24-hour day, including during sleep.

A low blood glucose reading is any reading below a patient’s physician-recommended target range. An occasionally low glucose reading is generally not a serious issue, but patients should discuss low readings with their physician, especially if readings are frequently or unusually low.

Treatment options for hypoglycemia

Managing diabetes can require patients to check their glucose (blood sugar) frequently with a glucose meter. Patients should ask their physician how often they need to test. A physician can also recommend a target blood glucose range. Glucose monitoring can tell people when their glucose is low and when they need to treat it.

It is important to note that the treatment of hypoglycemia associated with diabetes is complex, and all recommendations for treatment must be made by the physician providing diabetic care. Examples of various protocols for treating hypoglycemia in diabetic patients are given below. 

Glucose should be tested according to the physician-recommended schedule and whenever a patient suspects levels may be low. When hypoglycemia is confirmed, the patient should treat it immediately. If patients suspect low glucose but are unable to test, they should take steps to raise their glucose levels rather than wait until they can test later for confirmation.

It is highly recommended, for example, for people with diabetes who suspect hypoglycemia to check their glucose level before engaging in an activity that requires a high level of concentration. People should not drive if they suspect their glucose is low. The effects of low glucose on the autonomic nervous system and brain can increase a person’s risk of motor vehicle accidents. Patients with hypoglycemia unawareness (a condition in which the normal symptoms associated with low glucose are not felt or noticed) are instructed to always check their glucose before getting behind the wheel.

Likewise, it is advised that people immediately pull over into a safe location and test their glucose level when they begin to suspect low blood glucose. If their glucose reading is low, treatment to raise the blood sugar using the methods recommended by their physician is instituted, with a retest of their glucose level 15 minutes later. Individuals should not drive until their glucose levels are safe. A physician can recommend the glucose level that is safe for driving and how often a person should stop for glucose tests during long car trips.

Steps to raise glucose levels include:

  • Consuming some form of carbohydrate-rich food. People with diabetes are advised to carry something containing sugar with them at all times. Hypoglycemia can be treated with 10 to 15 grams of carbohydrates. The American Diabetes Association (ADA) recommends an adult consume one of the following foods that contain the correct amount of carbohydrates:
    • 3 glucose tablets
    • ½ cup (118 milliliters [ml]) of fruit juice
    • 5 to 6 pieces of hard candy
    • Half a can of nondiet soda
    • 10 gumdrops
    • 2 teaspoons or large lumps of sugar
    • 2 tablespoons of raisins
    • 6 jellybeans
    • 1 tablespoon of honey or corn syrup
    • A 0.68-ounce (19-gram) tube of cake-decorating gel
    • 1 cup (237 ml) of skim milk
    • One dose of glucose gel  
  • Glucagon injection. It is important to treat low glucose quickly, because without treatment a person can faint. When a person cannot swallow or is unconscious, an immediate injection of glucagon is often the recommendation. Normally produced by the pancreas, glucagon is a hormone that raises glucose. An injectable form is available by prescription.

    People with diabetes are advised to establish a sick-day plan with their physician including emergency plans to use glucagon should they ever need it. Such preparation includes training of people who may need to administer the medication, such as family, friends, teachers and coworkers. If glucagon is not available, emergency services will need to be alerted. Treatment of severe hypoglycemia in a hospital typically includes intravenous administration of glucose.

Experts advise that people with diabetes who have lost consciousness because of low glucose should:

  • Have emergency help called
  • Be injected with glucagon
  • Not be injected with insulin
  • Not be given food or fluids by mouth
  • Not have hands placed in their mouth

People with diabetes who take insulin are also advised to wear a medical identification bracelet or necklace at all times. Patients can also carry a medical identification card in their wallet to alert family, friends, teachers, coworkers and emergency personnel.

A physician may prescribe certain other medications to treat hypoglycemia. For example, diazoxide (Proglycem) can treat hypoglycemia that is due to overproduction of insulin. Diazoxide can interact with many other medications including antihypertensives, heart medications and antidepressants. Medical conditions that may affect its use include vascular, liver and kidney diseases.

Hypoglycemia may lead a physician to adjust an individual’s diabetes care plan, which could include exercise, diet or insulin schedule. For instance, patients may be advised to exercise in the morning rather than the evening and to perform glucose monitoring before, during and after exercise. Some antidiabetic agents, such as biguanides (metformin), are less likely to cause hypoglycemia than others such as sulfonylureas and meglitinides.

A registered dietitian may suggest approaches such as eating several small meals throughout the day and favoring fiber-rich complex carbohydrates over sugars and starches that may induce glucose to spike and fall.

Some treatments can help prevent hypoglycemia over the long term. Insulin pumps often improve glucose control for patients who require insulin therapy. The U.S. Food and Drug Administration in 2006 approved a device that combines an insulin pump with a continuous glucose monitor.

Some insulin-dependent patients may be candidates for a pancreas transplant or islet cell transplant. In its second annual report, the Collaborative Islet Transplant Registry indicated in 2005 that dangerous bouts of low glucose were rare in islet cell recipients. Interested individuals are advised to ask their physician if such treatments could be an option for them.

Assistance animals may be an option for some patients with hypoglycemia unawareness or hard-to-resolve hypoglycemia. Several organizations train dogs to sense irregular levels of glucose and alert their owner or other people. However, demand for these dogs is reported to far outstrip the supply.

Researchers are developing a noninvasive device to predict the onset of hypoglycemia. It consists of a chest-belt transmitter unit and a hand-held receiver.

In addition, researchers are working on drug treatments. Experimental medications block an enzyme called PARP-1 that may be involved in brain damage caused by hypoglycemia. Theoretically, however, such drugs might impede repair of DNA. 

Recent research on rats suggests that pyruvate, a byproduct of glucose metabolism, may prevent hypoglycemic brain damage. According to the scientists involved, pyruvate holds promise in treating humans, apparently without the potential disadvantage of the PARP-1 inhibitors. They hope to conduct clinical trials after further research on animals.

Prevention methods for hypoglycemia

Good diabetes management is the most effective way to prevent hypoglycemia. Patients should follow their physician- recommended schedule of diet, exercise and insulin or other diabetes medication (antidiabetic agents).

People with diabetes should try to determine what triggers their low blood glucose so they can report this to their physician, who will then adjust their diabetes management plan so as to maintain blood glucose in the target range. Keeping a record can help diabetes patients and their physicians spot patterns and anticipate potential problems. Despite these efforts, low blood glucose can still occur.

Steps to prevent hypoglycemia include:

  • Taking the physician-recommended dosage of insulin or other diabetes medication. If a patient frequently experiences low blood glucose, the medication dosage may be too high and the physician may decide to adjust it.
  • Balancing exercise with food intake and medication dosage. Exercising harder or longer than usual can result in low blood glucose. Patients can compensate for the extra activity with less medicine or more food.
  • Balancing food intake with medication. Eating too little food for the amount of medication taken can result in low blood glucose.
  • Eating at physician-recommended times. Patients should avoid delaying or skipping a meal or snack. Meals are planned around insulin peaks, and the insulin processes the glucose from food for energy. The body must have food in it for the insulin to process glucose.
  • Eating enough carbohydrates. The majority of glucose in the blood after a meal comes from the carbohydrates in food. The more carbohydrates a person eats, the more glucose is in the blood.
  • Drinking a limited amount of alcohol and only on a full stomach. Consuming alcohol, however, is not safe for everyone. Alcohol can promote the onset of serious diabetic complications or make existing complications worse. Patients should discuss the risks of drinking alcohol with their physician.
  • Talking to a physician or pharmacist about nondiabetes medication. Certain medications can lower blood glucose and cause hypoglycemia unawareness, a condition in which the normal symptoms of low glucose are not felt or noticed.

Questions for your doctor about hypoglycemia

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about hypoglycemia:

  1. What is my blood glucose level, and what range should it be in?
  2. Do I have, or am I at risk of developing, hypoglycemia?
  3. Do I or could I have hypoglycemia unawareness?
  4. What health risks does hypoglycemia pose for me?
  5. At what point is my glucose level considered hypoglycemic?
  6. How often should I check my blood sugar, and at what times of the day?
  7. Do I need to check my blood sugar before driving or during long car trips?
  8. Should I get up at night to check for nighttime hypoglycemia?
  9. How often should I have you or another health professional test my blood sugar?
  10. Should I be concerned about an occasional episode of hypoglycemia?
  11. Do you want me to report all episodes of hypoglycemia to you, or just frequent or unusual ones?
  12. Could any of my medications be contributing to my hypoglycemia?
  13. How do my diet and exercise habits affect my risk of hypoglycemia?
  14. What are my treatment options for hypoglycemia? Should I eat a certain amount of sugar when I experience an episode?
  15. Should I carry a glucagon kit? If so, who should be trained in administering the glucagon, and where can this training take place?
  16. Should I wear a medical ID tag? What should it say?
  17. Is my hypoglycemia significant enough to require changes in my diabetes management plan? If so, what do you recommend?
  18. Could I be candidate for an insulin pump, pancreas transplant or islet cell transplant?
  19. How can I help prevent hypoglycemia?
  20. How do I avoid overcompensating and developing hyperglycemia?
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