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.

When you think about diabetes and blood glucose control, the first thing that comes to mind is probably avoiding high blood glucose levels. After all, the hallmark of diabetes is high blood glucose, or hyperglycemia. But controlling blood glucose is more than just managing the “highs”; it also involves preventing and managing “lows,” or hypoglycemia.

Most people are aware that keeping blood glucose levels as close to normal as possible helps prevent damage to the blood vessels and nerves in the body. But keeping blood glucose levels near normal can carry some risks as well. People who maintain “tight” blood glucose control are more likely to experience episodes of hypoglycemia, and frequent episodes of hypoglycemia—even mild hypoglycemia and even in people who don’t keep blood glucose levels close to normal—deplete the liver of stored glucose (called glycogen), which is what the body normally draws upon to raise blood glucose levels when they are low. Once liver stores of glycogen are low, severe hypoglycemia is more likely to develop, and research shows that severe hypoglycemia can be harmful. In children, frequent severe hypoglycemia can lead to impairment of intellectual function. In children and adults, severe hypoglycemia can lead to accidents. And in adults with cardiovascular disease, it can lead to strokes and heart attacks.

To keep yourself as healthy as possible, you need to learn how to balance food intake, physical activity, and any diabetes medicines or insulin you use to keep your blood glucose as close to normal as is safe for you without going too low. This article explains how hypoglycemia develops and how to treat and prevent it.

What is hypoglycemia?
Blood glucose levels vary throughout the day depending on what you eat, how active you are, and any diabetes medicines or insulin you take. Other things, such as hormone fluctuations, can affect blood glucose levels as well. In people who don’t have diabetes, blood glucose levels generally range from 65 mg/dl to 140 mg/dl, but in diabetes, the body’s natural control is disrupted, and blood glucose levels can go too high or too low. For people with diabetes, a blood glucose level of 70 mg/dl or less is considered low, and treatment is recommended to prevent it from dropping even lower.

Under normal circumstances, glucose is the brain’s sole energy source, making it particularly sensitive to any decrease in blood glucose level. When blood glucose levels drop too low, the body tries to increase the amount of glucose available in the bloodstream by releasing hormones such as glucagon and epinephrine (also called adrenaline) that stimulate the release of glycogen from the liver.

Some of the symptoms of hypoglycemia are caused by the brain’s lack of glucose; other symptoms are caused by the hormones, primarily epinephrine, released to help increase blood glucose levels. Epinephrine can cause feelings of weakness, shakiness, clamminess, and hunger and an increased heart rate. These are often called the “warning signs” of hypoglycemia. Lack of glucose to the brain can cause trouble concentrating, changes in vision, slurred speech, lack of coordination, headaches, dizziness, and drowsiness. Hypoglycemia can also cause changes in emotions and mood. Feelings of nervousness and irritability, becoming argumentative, showing aggression, and crying are common, although some people experience euphoria and giddiness. Recognizing emotional changes that may signal hypoglycemia is especially important in young children, who may not be able to understand or communicate other symptoms of hypoglycemia to adults. If hypoglycemia is not promptly treated with a form of sugar or glucose to bring blood glucose level up, the brain can become dangerously depleted of glucose, potentially causing severe confusion, seizures, and loss of consciousness.

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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