Hypoglycemia occurs when your blood sugar (glucose) level falls too low. There are several reasons why this may happen, the most common is a side effect of drugs used to treat diabetes.
Blood sugar regulation
But to understand how hypoglycemia happens, it helps to know how your body normally processes blood sugar. When you eat, your body breaks down carbohydrates from foods â such as bread, rice, pasta, vegetables, fruit and milk products â into various sugar molecules, including glucose.
Glucose is the main energy source for your body, but it can't enter the cells of most of your tissues without the help of insulin â a hormone secreted by your pancreas. When glucose levels rise, certain cells (beta cells) in your pancreas release insulin. This allows glucose to enter the cells and provide the fuel your cells need to function properly. Any extra glucose is stored in your liver and muscles in the form of glycogen.
If you haven't eaten for several hours and your blood sugar level drops, another hormone from your pancreas called glucagon signals your liver to break down the stored glycogen and release glucose back into your bloodstream. This keeps your blood sugar level within a normal range until you eat again.
Aside from your liver breaking down glycogen into glucose, your body also has the ability to manufacture glucose. This process occurs primarily in your liver, but also in your kidneys.
Possible causes, with diabetes
People with diabetes may not make enough insulin (type 1 diabetes) or may be less responsive to it (type 2 diabetes). As a result, glucose tends to build up in the bloodstream and may reach dangerously high levels. To correct this problem, someone with diabetes may take insulin or other drugs to lower blood sugar levels.
But too much insulin or other diabetes medications may cause your blood sugar level to drop too low, causing hypoglycemia. Hypoglycemia may also happen if you don't eat as much food as usual after taking diabetes medication, or if you exercise more than you normally would.
Possible causes, without diabetes
Hypoglycemia in people without diabetes is much less common. Causes may include the following:
- Medications. Taking someone else's oral diabetes medication accidentally is a possible cause of hypoglycemia. Other medications may cause hypoglycemia, especially in children or in people with kidney failure. One example is quinine (Qualaquin), which is used to treat malaria.
- Excessive alcohol consumption. Drinking heavily without eating can block your liver from releasing stored glucose into your bloodstream, causing hypoglycemia.
- Some critical illnesses. Severe illnesses of the liver, such as severe hepatitis, can cause hypoglycemia. Disorders of the kidney, which can keep your body from properly excreting medications, can affect glucose levels due to a buildup of those medications. Long-term starvation, as may occur in the eating disorder anorexia nervosa, can result in the depletion of substances your body needs to generate glucose (gluconeogenesis), causing hypoglycemia.
- Insulin overproduction. A rare tumor of the pancreas (insulinoma) may cause overproduction of insulin, resulting in hypoglycemia. Other tumors may result in excessive production of insulin-like substances. Enlargement of beta cells of the pancreas that produce insulin (nesidioblastosis) may result in excessive insulin release, causing hypoglycemia.
- Hormone deficiencies. Certain disorders of the adrenal glands and the pituitary gland can result in a deficiency of key hormones that regulate glucose production. Children may experience hypoglycemia if they have a deficiency of growth hormone.
Hypoglycemia after meals
Hypoglycemia usually occurs when you haven't eaten (when you're in a fasting state), but that's not always the case. Sometimes hypoglycemia occurs after meals because the body produces more insulin than is needed.
This type of hypoglycemia, called reactive or postprandial hypoglycemia, may occur in people who have had stomach surgery. It may also occur in people who haven't had this surgery.