Spotting The Signs - Understanding Hypoglycemia: Diabetes

Content provided by the Faculty of the Harvard Medical School

Spotting the signs

Many experts associate hypoglycemic reactions with blood sugar levels below 60 mg/dL, but it's difficult to pinpoint the level at which hypoglycemia symptoms occur because each person responds differently. For instance, your blood sugar might fall below 40 mg/dL without causing any symptoms, while someone else might feel symptoms coming on when his or her blood glucose falls below 70 mg/dL.

Over time, the symptoms often become subtler, especially among people with type 1 diabetes. Eventually, for example, you may not experience the palpitations, sweating, and anxiety that once characterized the condition. Instead, your first symptom may be fuzzy thinking. Some people develop a condition, termed hypoglycemia unawareness, in which they experience no warning symptoms even when their blood sugar levels are very low.

Low blood sugar usually sets off alarms in many organ systems. The brain, which relies on glucose to function, is especially sensitive to sugar deprivation. The first signs of hypoglycemia resemble those of an anxiety attack because a decline in blood sugar affects the autonomic nervous system. Epinephrine (also known as adrenaline) is secreted, causing sweating, nervousness, trembling, palpitations, lightheadedness, and often hunger. The release of adrenaline is a corrective response to hypoglycemia because it stimulates your liver to make more sugar.

More profound levels of hypoglycemia affect brain function and result in fatigue, weakness, blurred vision, dizziness, slurred speech, and confusion and other behavior that resembles inebriation, such as belligerence or silliness. A further drop in blood sugar levels or failure to promptly treat the condition may result in loss of consciousness, seizures, and even death (see "Severe hypoglycemia"). Rarely, an episode of hypoglycemia while driving may cause a serious car accident.

Not everyone experiences all these symptoms, and it can be hard to tell the difference between hypoglycemia and anxiety over a problem at work or an argument with your spouse. In addition, beta blockers (used to treat high blood pressure and heart disease) and alcohol can exacerbate hypoglycemia by masking early symptoms. Therefore, they must be used cautiously.

If hypoglycemia occurs during sleep, the only clues may be damp pajamas (from sweating), vivid nightmares, or a nagging headache on awakening. It's important to be attuned to these early signs and to know what blood sugar levels set off hypoglycemia.

Last updated:	January 23, 2007