A patient has asked me to write about hypoglycemia. The word originates from the Greek elements hypo- meaning "under," glykys meaning "sweet," and haema meaning "blood." We have come to know hypoglycemia as low blood sugar.

To understand hypoglycemia, one first has to learn how blood sugar is regulated in the body. When we eat carbohydrates, they are broken down into smaller sugars in the digestive tract and enter the bloodstream. Glucose is the main sugar our cells use for energy.

When the level of glucose rises in the bloodstream following a meal, it stimulates secretion of insulin by the pancreas, an organ found in the upper abdomen. Insulin is required to let glucose enter our cells to be used for energy. As glucose enters the cells, the level goes down in the blood and the secretion of insulin goes back to baseline.

The level of glucose in the bloodstream is very tightly controlled. Normal values range from 70-110 mg/dL (milligrams per deciliter). Diabetes is defined as having elevated blood glucose levels. Hypoglycemia is defined as having a blood glucose less than 50 mg/dL in men, less than 45 mg/dL in women, and less than 40 mg/dL in infants and children.

Hypoglycemia is most commonly found in people with diabetes. This usually occurs when they take too much diabetic medication or insulin and/or don't eat properly. Unusual amounts of exercise can also burn up glucose and lead to lower levels.

Many non-diabetic medications can also result in hypoglycemia. The most commonly implicated ones are aspirin, some anti-depressants, sulfa drugs and diuretics. Alcohol can also lower blood sugar.

Any condition that causes the body to burn glucose excessively can also result in hypoglycemia. Infections can do this as can hyperthyroidism, a condition resulting in increased metabolism. Excessive exercise with inadequate intake of calories can cause hypoglycemia. Pregnancy is also common cause as is just not eating properly.

One specific type of hypoglycemia that we frequently diagnose is called "reactive hypoglycemia." This is an abnormal response of the body to the consumption of sugar. Some people who eat meals very high in carbohydrates, especially simple sugars, are prone to this condition. Eating these foods causes a rapid rise in blood glucose. This stimulates the pancreas to make too much insulin. This in turn lowers the blood glucose too much. The pancreas overreacts, hence the name "reactive" hypoglycemia.

Neurologic symptoms of hypoglycemia can include headache, confusion or "brain fog," dizziness and personality changes. Severe hypoglycemia can cause seizures or coma. Since glucose is the only energy source the brain can use (the rest of the body can burn fats and proteins), low levels can cause severe brain injury.

When glucose levels are low, the body produces adrenaline that causes the release of stored glucose in the body. This adrenaline rush can cause sweating, anxiety, tremor and nervousness. Patients may also experience irregular heartbeats or palpitations as well as stomach cramps, diarrhea or nausea.

Diagnosis of hypoglycemia can often be made by history alone, especially if it occurs shortly after eating or if someone hasn't eaten in quite awhile and has symptoms. If the diagnosis is uncertain, lab testing can be done. This usually involves having a fasting blood glucose test, drinking a specified amount of glucose, and then checking blood glucose levels for a few hours thereafter.

Treatment of hypoglycemia is aimed at correcting the underlying cause(s). Diabetics may need adjustment in their medication, diet or exercise. Those who are on certain medications may need to have them adjusted or discontinued. Underlying infections or hormone problems like hyperthyroidism need to be treated.

For those folks who have idiopathic (cause undetermined) or reactive hypoglycemia, the foundation of treatment is dietary modification. Since these patients often overreact to diets high in carbohydrates, limiting concentrated sweets such as soda and candy is important. Since proteins and fats are digested more slowly and provide calories to the body more slowly, increasing them in the diet causes a slower rise in glucose levels after a meal. It's also important to try and eat smaller meals more frequently throughout the day. This keeps the levels of glucose entering the body more constant, avoiding wide swings in blood sugar.