Sign up for email updates


Back Pain & Osteoporosis
Coronary Heart Disease
Depression & Anxiety
Digestive Disorders
Heart Attack Prevention
Hypertension & Stroke
Lung Disorders
Nutrition & Weight Control
Prostate Disorders





Adrenaline-triggered symptoms: anxiety, hunger, a tingling sensation in the hands, palpitations, profuse perspiration, shakiness, or weakness. These symptoms may not occur in people taking beta-blocker drugs and in those with long-standing diabetes.

Symptoms of nighttime hypoglycemia: nightmares, restlessness, or profuse perspiration.

Slower-onset symptoms, due to inadequate supply of glucose to the brain: agitation, amnesia, confusion, dizziness, disorientation, feeling cold, headache, impaired vision, lack of coordination, numbness, or personality changes.

Emergency symptoms: seizures, temporary paralysis of one side of the body, or loss of consciousness.

When To Call Your Doctor

Call an ambulance immediately if someone loses consciousness.

Consult a doctor if you develop symptoms of hypoglycemia.

What Is It?

Hypoglycemia is an abnormally low blood sugar level, arising from an imbalance in the rates of glucose release from the liver and its use by other body tissues. Glucose (a simple sugar) is absolutely essential as an energy source for the cells of the central nervous system. Insulin regulates blood glucose levels by slowing the release of glucose by the liver and stimulating its entry into other cells. Low blood glucose levels trigger the release of adrenaline, which produces the symptoms of a hypoglycemic episode, characterized by a sudden attack of anxiety, shakiness, dizziness, hunger, and excessive perspiration. Such episodes are generally not dangerous, because the symptoms incite people to ingest a sugar-containing food or drink, and the adrenaline (and other hormones) released tend to help restore blood sugar levels to normal.

However, prolonged, severe hypoglycemia may be very dangerous, as it gradually and insidiously starves the brain of glucose, which may lead to disorientation and confusion, eventually progressing to seizures, partial paralysis, or loss of consciousness. If left untreated, hypoglycemia may ultimately result in permanent brain damage and, in rare cases, even death. There are two types of hypoglycemic episodes: those that occur two to five hours after eating, known as postprandial hypoglycemia, and those that occur after an extended period without food (usually overnight), known as fasting hypoglycemia.

Postprandial hypoglycemia may be unpleasant, but is usually not serious; it can be corrected easily by eating or drinking and by the action of hormones. Fasting hypoglycemia—which most commonly occurs among people with diabetes when too much insulin is administered—is potentially very dangerous, because of the risk of brain damage. In addition, people with long-standing diabetes often do not have typical symptoms of hypoglycemia. In many cases, however, hypoglycemia can be prevented by carefully following specific diet and lifestyle guidelines (see Diabetes Mellitus for more information).

What Causes It?

In most cases of postprandial hypoglycemia, the cause is unknown. It may occur, however, as one of the early manifestations of diabetes mellitus or following stomach surgery.

The most common cause of fasting hypoglycemia is the administration of too much insulin to a person with diabetes. Risk is increased when these patients exercise or miss meals.

Other causes of fasting hypoglycemia include excessive alcohol ingestion, insulin-producing tumors of the pancreas (insulinoma), tumors in other organs, adrenal or pituitary insufficiency, rampant leukemia, congestive heart failure, chronic kidney failure, severe liver failure, and some childhood metabolic disorders, such as fructose intolerance and galactosemia.

Occasionally, hypoglycemia may be triggered by excessive amounts of certain medications, including oral hypoglycemic agents, aspirin (especially among children), and beta-blockers.


People with diabetes should carefully follow their regimen of diet, medication, exercise, and blood glucose monitoring and should always carry some fast-acting carbohydrate (glucose tablets, hard candies, gumdrops, or fruit juice) to consume at the first sign of symptoms. Also, people with diabetes who use insulin should never drive or travel in a car, plane, or train without having some sort of carbohydrate food (such as peanut butter crackers) available for a snack.

Those who experience postprandial hypoglycemic episodes should eat five or six small meals a day that are low in simple carbohydrates and high in protein, fat, and fiber.


In those who do not have diabetes, diagnosis requires demonstration of low blood glucose levels accompanied by the usual symptoms. Depending on the type of hypoglycemia, blood glucose is measured either during a glucose tolerance test or after an overnight fast. Further tests and a detailed patient history are then necessary to determine the underlying cause of hypoglycemia.

Those with diabetes can verify and document episodes of hypoglycemia with home blood glucose monitoring.

How To Treat It

If you sense a hypoglycemic episode coming on, stop all activity. If you are driving a car, for example, pull over.

Consume one portion of any fast-acting carbohydrate: four ounces of fruit juice or sugared drink; some candy, such as six or seven jelly beans, or three large marshmallows; or one-half of a tube of Glutose (80 gram container). If you do not feel better quickly, consume one more portion. However, do not eat chocolate because the fat in it slows absorption of sugar into the bloodstream.

Instruct your family and friends to give you a small drink of fruit juice or to smear syrup inside your mouth if you become disoriented or uncooperative (symptoms of worsening hypoglycemia).

Show your family and friends how to administer an injection of glucagon, a hormone that helps raise your blood sugar level, in the event you lose consciousness from hypoglycemia. After the injection they should call an ambulance and, in the meantime, not attempt to give food or fluids and most certainly not administer insulin.

Your doctor may adjust or change your medication if you are receiving too much insulin or if you are taking one of the other drugs that sometimes triggers hypoglycemia in those who are susceptible.

Surgery is required to treat a pancreatic tumor (insulinoma) that causes hypoglycemia. This sometimes involves removing most of the pancreas. In cases where surgery is not an option, chemotherapy may be used to destroy cancerous cells.


From Johns Hopkins Symptoms and Remedies, the complete home medical reference. You can order this book now on our secure server.


Buy now


The Diabetes White Paper from The Johns Hopkins White Papers series is an annual, in-depth report written by Hopkins physicians.

Buy now
Johns Hopkins Symptoms and Remedies
An easy-to-use reference work that can help you pinpoint the cause of hundreds of symptoms, from abdominal pain to skin rash to swollen glands.


    Contact us 
    © 2005 Medletter Associates, Inc.