What Is It?

Hypoglycemia is an abnormally low level of blood sugar (blood glucose). Because the brain depends on blood sugar as its primary source of energy, hypoglycemia interferes with the brain’s ability to function properly. This can result in dizziness, headache, blurred vision, difficulty concentrating and even more serious neurological symptoms. Hypoglycemia also triggers the release of epinephrine, norepinephrine and other body hormones that work to raise blood-sugar levels. The release of these hormones produces additional symptoms of tremor, sweating, rapid heartbeat, anxiety and hunger.

Hypoglycemia is most common in people with diabetes. In these people, hypoglycemia occurs because of some imbalance between their dose of diabetic medication, usually insulin, and their diet or exercise level. Because insulin and exercise both lower blood sugar and food raises it, hypoglycemia in diabetic patients can be caused by too much insulin, a switch to a new combination of insulins whose effects overlap, too little food, meal skipping, or too much exercise. Although hypoglycemia also can occur with the use of oral hypoglycemic medications that lower blood glucose, especially the sulfonylureas, it is much more common in people who are taking insulin.

True hypoglycemia with documented low blood sugar rarely occurs in people who do not have diabetes. In these people, hypoglycemia can be caused by many different medical problems. A partial list includes:

  • Gastrointestinal surgery, usually involving removal of some part of the stomach, that has altered the normal relationships between digestion and insulin release
  • An insulinoma (a pancreatic tumor that secretes insulin)
  • A deficiency of growth hormone from the pituitary gland or of cortisol from the adrenal glands, both of which help to maintain blood sugars in the normal range
  • Drugs or medications, such as alcohol, too much aspirin, quinine (used to treat malaria) and others
  • Severe liver disease
  • Self-administration of insulin by someone who does not have diabetes
  • Non-pancreatic tumors
  • A rare enzyme defect involving glucose-6-phosphatase, liver phosphorylase, pyruvate carboxylase or another enzyme


Hypoglycemia can cause:

  • Symptoms related to low levels of sugar supplying the brain — Headache, dizziness, blurred vision, difficulty concentrating, poor coordination, confusion, weakness or fainting, tingling sensations in the lips or hands, confused speech, abnormal behavior, convulsions, loss of consciousness, coma
  • Symptoms related to epinephrine and norepinephrine — Sweating, tremors (feeling shaky), rapid heartbeat, anxiety, hunger


If a person with diabetes is suffering from severe hypoglycemia, he or she may not be able to answer the doctor’s questions because of confusion or unconsciousness. In this case, a family member or close friend will need to describe the patient’s medical history and insulin regimen. To help ensure effective emergency treatment, all people with diabetes should consider wearing a medical alert bracelet or necklace. This potentially lifesaving jewelry will identify the patient as having diabetes, even if the patient is far from home and traveling alone. Family members or friends of a person with diabetes should learn how to bring a patient out of severe hypoglycemia by giving the person orange juice or another carbohydrate, or by giving an injection of glucagon.

If a person with diabetes can answer questions appropriately, the doctor will ask about his or her current insulin dosage, as well as recent food intake, exercise schedule and other medications. If the patient has been self-monitoring blood sugar with a glucometer (a hand-held device to measure glucose levels in blood from a finger prick), the doctor will review the most recent glucometer readings to confirm low blood sugar and to check for a pattern of hypoglycemia related to diet or exercise.

In people who do not have diabetes, the doctor will review current medications and ask about any history of gastrointestinal surgery (especially involving the stomach), liver disease and an enzyme deficit. Patients should describe their symptoms and when the symptoms occur — whether they occur before or after meals, while sleeping or following exercise.

In a person with diabetes, the diagnosis of hypoglycemia is based on symptoms and blood-sugar readings. In most cases, no further testing is necessary.

In a person who is not diabetic, the ideal time for diagnostic testing is during an episode of hypoglycemic symptoms. At that time, blood can be drawn to measure levels of glucose, and the patient’s reactions to glucose intake can be assessed. If these measures confirm the diagnosis of hypoglycemia, blood can be sent to a laboratory to measure insulin levels. If the patient has no symptoms at the time of evaluation, the doctor may ask him or her to measure his or her blood glucose when hypoglycemic symptoms occur, and obtain a blood sample that can be tested to measure liver function and cortisol levels. If an insulinoma is suspected, the doctor may order a 72-hour fast. During that period, blood levels of glucose and insulin will be measured every six hours. The diagnosis of insulinoma is highly likely if blood glucose is 70 milligrams per deciliter or lower and insulin levels are inappropriately high.

If a patient develops symptoms of hypoglycemia only after eating, the doctor may ask him or her to self-monitor blood sugar with a glucometer at the time the symptoms occur.

Expected Duration

An episode of hypoglycemia caused by exercise or by too much short-acting insulin usually can be stopped within minutes by ingesting a food or beverage that contains sugar (sugar tablets, candy, orange juice, nondiet soda). Hypoglycemia caused by sulfonylurea or long-acting insulin can take days to resolve.

People with diabetes remain at risk for episodes of hypoglycemia throughout life because they need medications that lower blood sugar. About 85 percent of patients with an insulinoma will be cured of hypoglycemia once the insulin-secreting tumor is removed. In many people without diabetes who have symptoms of hypoglycemia, the symptoms can persist for a long time, and often they are caused by something other than low blood-glucose levels.


In patients taking insulin, drinking alcohol can lead to an episode of hypoglycemia. Patients with diabetes should discuss with their doctors how much alcohol, if any, they can drink safely. Alcohol can cause serious episodes of hypoglycemia even when insulin was taken hours before. People with diabetes should be very aware of this possible problem if they decide to drink.

People with diabetes should always have ready access to emergency supplies for treating unexpected episodes of hypoglycemia. These supplies may include candy, sugar tablets, sugar paste in a tube and/or a glucagon injection kit. A glucagon injection may be given if a hypoglycemic patient is unconscious and cannot take sugar by mouth. For diabetic children, emergency supplies can be kept in the school nurse’s office.

Any person at risk of hypoglycemic episodes can help to avoid attacks by learning about his or her condition and sharing this knowledge with friends and family members. The person also should eat at regular times during the day, never skip meals and maintain a consistent exercise level. Like people with diabetes, nondiabetic people with hypoglycemia should always have ready access to a source of sugar. As a safety backup, a doctor may prescribe a glucagon emergency kit for nondiabetic people who have a history of becoming disoriented or losing consciousness from hypoglycemia.


If a conscious patient is having symptoms of hypoglycemia, the symptoms usually resolve if something sweet (sugar tablets, candy, juice, nondiet soda) is taken by mouth. An unconscious patient can be treated with an immediate injection of glucagon or with intravenous glucose infusions in a hospital setting.

People with diabetes who have hypoglycemic episodes may need modifications in their insulin dosage, diet or exercise regimen.

Even of you recognize that your symptoms are caused by hypoglycemia, you should treat yourself or seek treatment, and not try to just “tough it out.” Some people with diabetes lose the ability to recognize the symptoms of hypoglycemia (hypoglycemic unawareness), which can be very serious because they may not know to seek treatment. Hypoglycemia unawareness can be a severe problem, but it can be reversed significantly if a person with this problem understands its causes and how it can be prevented.

An insulinoma is treated by removing the tumor surgically. Hypoglycemia caused by problems with the adrenal or pituitary glands is treated by replacing the missing hormones with medication. Nondiabetic people with hypoglycemic symptoms following meals are treated by modifying their diet. They usually need to eat frequent, small meals and avoid fasting.

When To Call A Professional

Call for emergency medical assistance whenever anyone is unconscious or obviously disoriented. Severe insulin reactions can be fatal, so it is important to seek treatment immediately.

People with diabetes should contact their doctors promptly if they experience frequent episodes of hypoglycemia. They may need to adjust their daily doses of insulin, oral hypoglycemic medication or their meal plans.

Nondiabetic people who experience symptoms of hypoglycemia should contact their doctors as soon as possible for evaluation of the problem.


In people with diabetes, the prognosis is excellent if they adhere to their prescribed insulin dosage, recommended diet and exercise guidelines.

Most patients with insulinomas can have them removed successfully by surgery. However, in about 15 percent of these patients, the insulinoma is cancerous and has spread, so it cannot be removed completely. These patients still suffer from hypoglycemia after surgery.

Most patients with other forms of hypoglycemia can be successfully treated with dietary modifications.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.