Diagnosis
To diagnose hypoglycemia in people who do not have diabetes, the doctor looks for the following three conditions:
- The patient complains of symptoms of hypoglycemia
- Blood glucose levels are measured while the person is experiencing those symptoms and found to be 45 mg/dL or less in a woman or 55 mg/dL or less in a man
- The symptoms are promptly relieved upon ingestion of sugar.
The doctor will also check the patient for health conditions such as diabetes, obtain a medication history, and assess the degree and severity of the patient's symptoms. Laboratory tests to measure insulin production and levels of C-peptide (a substance that the pancreas releases into the bloodstream in equal amounts to insulin) may be performed.
Reactive Hypoglycemia
A diagnosis of reactive hypoglycemia is considered only after other possible causes of low blood sugar have been ruled out. Reactive hypoglycemia with no known cause is a condition in which the symptoms of low blood sugar appear 2 to 5 hours after eating foods high in glucose.
Ten to 20 years ago, hypoglycemia was a popular diagnosis. However, studies now show that this condition is actually quite rare. In these studies, most patients who experienced the symptoms of hypoglycemia after eating glucose-rich foods consistently had normal levels of blood sugar--above 60 mg/dL. Some researchers have suggested that some people may be extra sensitive to the body's normal release of the hormone epinephrine after a meal.
People with symptoms of reactive hypoglycemia unrelated to other medical conditions or problems are usually advised to follow a healthy eating plan. The doctor or dietitian may suggest that such a person avoid foods high in carbohydrates; eat small, frequent meals and snacks throughout the day; exercise regularly; and eat a variety of foods, including whole grains, vegetables, and fruits.
Rare Causes of Hypoglycemia
Fasting hypoglycemia occurs when the stomach is empty. It usually develops in the early morning when a person awakens. As with other forms of hypoglycemia, the symptoms include headache, lack of energy, and an inability to concentrate. Fasting hypoglycemia may be caused by a variety of conditions such as hereditary enzyme or hormone deficiencies, liver disease, and insulin-producing tumors.
In hereditary fructose intolerance, a disorder usually seen in children, the body is unable to metabolize the natural sugar fructose. Attacks of hypoglycemia, marked by seizures, vomiting, and unconsciousness, are treated by giving glucose and eliminating fructose from the diet.
Galactosemia, a rare genetic disorder, hampers the body's ability to process the sugar galactose. An infant with this disorder may appear normal at birth, but after a few days or weeks of drinking milk (which contains galactose), the child may begin to vomit, lose weight, and develop cataracts. The liver may fail to release stored glycogen into the blood, triggering hypoglycemia. Removing milk from the diet is the usual treatment.
A deficiency of growth hormone causes increased sensitivity to insulin. This sensitivity occurs because growth hormone opposes the action of insulin on muscle and fat cells. For this reason, children with growth hormone deficiency sometimes suffer from hypoglycemia, which goes away after treatment.
People with insulin-producing tumors, which arise in the islet cells of the pancreas, suffer from severe episodes of hypoglycemia.
To diagnose these tumors, called insulinomas, a doctor will put the patient on a 24- to 72-hour fast while measuring blood levels of glucose, insulin, and proinsulin. High levels of insulin and proinsulin in the presence of low levels of glucose strongly suggest an insulin-producing tumor. These tumors are usually benign and can be surgically removed.
In rare cases, some cancers such as breast cancer and adrenal cancer may cause hypoglycemia through secretion of a hormone called insulin-like growth factor II. The treatment is removal of the tumor, if possible.
