Updated July 25, 2006

Understanding Hypoglycemia

by Laura Hieronymus, M.S.Ed., A.P.R.N., B.C.-A.D.M., C.D.E., and Belinda O’Connell, M.S., R.D., C.D.E.

Who is at risk?
Some people are at higher risk of developing hypoglycemia than others. Hypoglycemia is not a concern for people who manage their diabetes with only exercise and a meal plan. People who use insulin or certain types of oral diabetes medicines have a much greater chance of developing hypoglycemia and therefore need to be more careful to avoid it. Other risk factors for hypoglycemia include the following:

• Maintaining very “tight” (near-normal) blood glucose targets.
• Decreased kidney function. The kidneys help to degrade and remove insulin from the bloodstream. When the kidneys are not functioning well, insulin action can be unpredictable, and low blood glucose levels may result.
• Alcohol use.
• Conditions such as gastropathy (slowed stomach emptying) that cause variable rates of digestion and absorption of food.
• Having autonomic neuropathy, which can decrease symptoms when blood glucose levels drop. (Autonomic neuropathy is damage to nerves that control involuntary functions.)
• Pregnancy in women with preexisting diabetes, especially during the first trimester.

A side effect of diabetes treatment
Hypoglycemia is the most common side effect of insulin use and of some of the oral medicines used to treat Type 2 diabetes. How likely a drug is to cause hypoglycemia and the appropriate treatment for hypoglycemia depends on the type of drug.

Secretagogues. Oral medicines that stimulate the pancreas to release more insulin, which include sulfonylureas and the drugs nateglinide (brand name Starlix) and repaglinide (Prandin), have the potential side effect of hypoglycemia. Sulfonylureas include glimepiride (Amaryl), glipizide (Glucotrol and Glucotrol XL), and glyburide (DiaBeta, Micronase, and Glynase).

Sulfonylureas are taken once or twice a day, in the morning and the evening, and their blood-glucose-lowering effects last all day. If you miss a meal or snack, the medicine continues to work, and your blood glucose level may drop too low. So-called sulfa antibiotics (those that contain the ingredient sulfamethoxazole) can also increase the risk of hypoglycemia when taken with a sulfonylurea. Anyone who takes a sulfonylurea, therefore, should discuss this potential drug interaction with their health-care provider should antibiotic therapy be necessary.

Nateglinide and repaglinide are taken with meals and act for only a short time. The risk of hypoglycemia is lower than for sulfonylureas, but it is still possible to develop hypoglycemia if a dose of nateglinide or repaglinide is taken without food.

Insulin. All people with Type 1 diabetes and many with Type 2 use insulin for blood glucose control. Since insulin can cause hypoglycemia, it is important for those who use it to understand how it works and when its activity is greatest so they can properly balance food and activity and take precautions to avoid hypoglycemia. This is best discussed with a health-care provider who is knowledgeable about you, your lifestyle, and the particular insulin regimen you are using.

Biguanides and thiazolidinediones. The biguanides, of which metformin is the only one approved in the United States, decrease the amount of glucose manufactured by the liver. The thiazolidinediones, pioglitazone (Actos) and rosiglitazone (Avandia), help body cells become more sensitive to insulin. The risk of hypoglycemia is very low with these medicines. However, if you take metformin, pioglitazone, or rosiglitazone along with either insulin or a secretagogue, hypoglycemia is a possibility.

Laura Hieronymus is the program coordinator/nurse educator for Drs. Borders and Associates, PSC, an American Diabetes Association–recognized education service in Lexington, Kentucky. Belinda O’Connell is a Diabetes Nutrition Specialist at the International Diabetes Center in Minneapolis, Minnesota, and a freelance health and science writer.

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