Hypoglycemia
A primer on diagnosis, prevention and treatment
Hypoglycemia is an abnormally low level of blood sugar (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 neurologic symptoms. Hypoglycemia also triggers the release of epinephrine, norepinephrine and other hormones that work to raise blood sugar levels. The release of these hormones produces symptoms of tremor, sweating, rapid heartbeat, anxiety and hunger.
Hypoglycemia is most common in persons with diabetes 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 that have overlapping effects; too little food; meal skipping or too much exercise. Although hypoglycemia can also occur with the use of oral hypoglycemic medications to lower blood glucose (sugar-lowering medications taken by mouth, not by injection), especially the sulfonylureas, it is much more common in people who take insulin.
Only about one percent of cases of hypoglycemia occur in patients who do not have diabetes. In these individuals, hypoglycemia may 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 or of cortisol from the adrenals, which help to maintain blood sugars in the normal range
- Drugs or medications, such as alcohol, propranolol, aspirin (overdose), quinine (to treat malaria) and others
- Severe liver disease
- Self-administration of insulin
- Nonpancreatic tumors
- Rare enzyme defects involving glucose 6-phosphatase, liver phosphorylase, pyruvate carboxylase or another enzyme
Hypoglycemia may cause:
- Symptoms related to low levels of sugar supplying the brain: Headache, dizziness, blurred vision, difficulty concentrating, poor coordination, confusion, weakness or fainting, confused speech, abnormal behavior, convulsions, loss of consciousness, coma
- Symptoms related to release of epinephrine and norepinephrine: Sweating, tremors (feeling shaky), rapid heartbeat, anxiety, hunger, tingling sensations in the lips
Sometimes, there may be no symptoms. People who've had diabetes for a long time may no longer release responsive hormones when hypoglycemia occurs. This places them at especially high risk because warning signs and symptoms no longer appear, a phenomenon termed "hypoglycemia unawareness."
What your doctor looks for
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 wear 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.
If a patient with diabetes can answer questions appropriately, the doctor will ask about their current insulin dosage, 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 blood glucose levels from a fingerprick), 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 patients who do not have diabetes, the doctor will review their current medications and ask about any history of gastrointestinal surgery (especially involving the stomach), and liver disease. Patients should describe their symptoms and when they occur (for example, before or after meals, while sleeping or after exercise).
Diagnosis
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. 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 response of the patient to glucose administration can be assessed.
In a person who does not have diabetes, if blood tests confirm the diagnosis of hypoglycemia, blood can be sent to measure insulin. If the patient has no symptoms at the time of evaluation, the doctor may ask her to measure her blood glucose when she is having hypoglycemic symptoms. Blood would be obtained 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 are measured every six hours. A diagnosis of insulinoma is likely in a patient whose blood glucose level is 70 mg/dL or below in association with inappropriately high insulin levels.
If a patient develops symptoms of hypoglycemia only after eating, the doctor may ask her to self-monitor her blood sugar with a glucometer at the time of the hypoglycemic symptoms.
Expected duration
An episode of hypoglycemia can usually be stopped within minutes by ingesting a food or beverage that contains sugar (sugar tablets, candy, orange juice, non-diet soda).
Episodes of hypoglycemia are often terminated spontaneously by the body's release of epinephrine and glucagon, substances that raise blood glucose levels. But hypoglycemia can be prolonged by the failure to secrete glucagon in people who've had diabetes for many years.
Unfortunately, because of their need for medications that lower blood sugar, people with diabetes remain at risk for episodes of hypoglycemia throughout life. About 85 percent of patients with an insulinoma are cured of hypoglycemia once the insulin-secreting tumor is removed surgically. In many people without diabetes but with symptoms resembling those of hypoglycemia, the symptoms may persist for a long time, but often they are not due to low blood glucose levels.
Prevention
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 (glucagon is a hormone that raises blood sugar). A glucagon injection may be given if a hypoglycemic patient is unconscious and cannot take sugar by mouth. Emergency supplies can be kept in a large purse, in a briefcase or in the school nurse's office (for children with diabetes).
In general, any patient at risk for hypoglycemic episodes can help avert attacks by learning about her condition and sharing this knowledge with friends and family members. She should also eat at regular times during the day, never skip meals and maintain a consistent exercise level. Whether or not they have diabetes, people who experience episodes of 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.
Treatment
Symptoms of hypoglycemia in a conscious person usually resolve if something sweet (sugar tablets, candy, juice, nondiet soda) is taken by mouth. An unconscious person 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 to modify in their insulin dosage, diet or exercise regimen.
An insulinoma is treated by surgical removal of the tumor. Hypoglycemia due to adrenal or pituitary insufficiency is treated with hormone replacements. Nondiabetic people with hypoglycemic symptoms following meals are treated with dietary modification, usually frequent, small meals.
When to call your doctor
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 doctor promptly if they experience frequent episodes of hypoglycemia. They may need to have an adjustment in their dose of insulin or oral hypoglycemic medication or in their meal plan.
Nondiabetic people who experience symptoms of hypoglycemia should also contact their doctor as soon as possible for evaluation of their complaints.
Prognosis
In patients 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 successfully removed by surgery. However, in about 15 percent of the patients, the insulinoma is malignant and has spread, so it cannot be totally removed; these people will still suffer from hypoglycemia. Most people with other forms of hypoglycemia can be treated successfully with dietary modifications.
Additional information
For more information on hypoglycemia, you can contact:
National Diabetes Information Clearinghouse
1 Information Way
Bethesda, MD 20892-3560
Phone: 800 860-8747
http://diabetes.niddk.nih.gov/dm/pubs/hypoglycemia/
Updated: April 2006
