Hypoglycemia (Low Blood Sugar)
Glucose is a type of sugar (carbohydrate). It is the body's main source of fuel. When the level of glucose in the blood becomes too low, it is called hypoglycemia. If the glucose levels are too low the body can not function properly.
Glucose in Blood
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is the most common cause particularly when combined with the following factors:
Taking too much blood sugar-lowering medication Delaying or missing meals, or eating too little at meals Too much or too strenuous exercise
Reactive hypoglycemia may also occur in people without diabetes. It is now thought to be quite rare.
Other causes of hypoglycemia include:
Drinking too much alcohol (especially binge drinking coupled with not eating) Prolonged fasting Early pregnancy Long periods of strenuous exercise Certain medications may increase the risk of hypoglycemia (people on beta blockers who exercise, aspirin in children) Certain pituitary or adrenal gland conditions Certain liver conditions Certain types of stomach surgery Certain autoimmune conditions Hereditary enzyme or hormone deficiencies A reaction to certain foods (rarely, eating unripe ackee fruit from Jamaica) Pancreatic tumors Tumors that produce an insulin-like hormone
Any severe or protracted illness, such as:
Factors that can increase your risk for hypoglycemia include:
Fasting, particularly in combination with strenuous exercise Family history of hypoglycemia
Symptoms may come on slowly or suddenly.
Sweating Nervousness Feeling faint Heart palpitations Hunger Headache
As hypoglycemia worsens symptoms may include:
Fatigue Dizziness Weakness Inappropriate behavior or severe confusion Loss of consciousness
The doctor will ask about your symptoms and medical history. A physical exam will be done.
If hypoglycemia is suspected, your doctor will try to document your low blood sugar. Your blood glucose levels will be measured while you are having symptoms.
If this is not possible, you may have a glucose tolerance test. This is a series of blood tests after taking glucose by mouth.
Other, less routine tests include:
Laboratory tests for antibodies to insulin
Imaging tests to check for a tumor, such as:
—a test that uses radio waves and magnetic fields to make pictures of structures inside the body
CT scan—a type of x-ray that uses a computer to make pictures of structures inside the body Ultrasound—a test that uses sound waves to make pictures of structures inside the body
Symptoms of low blood sugar can be relieved quickly by:
Eating sugar in a rapidly absorbable form, such as:
Fruit Fruit juice Sugared soft drink Table sugar in water Candy Taking glucose tablets IV glucose (in severe cases)
Some people who have prolonged or severe hypoglycemia take glucagon. Glucagon is an injectable hormone. It raises blood sugar levels.
It can be used in emergencies when people have a severe reaction. It can be used if the person cannot take sugar by mouth.
Hypoglycemia may be caused by a tumor. In this case a surgery to remove the tumor may be needed.
Measures that can help prevent hypoglycemia include:
Monitor your medicine. Take it as prescribed. Follow the diet and exercise plans given by your doctor. Avoid drinking alcohol in excess. Avoid drinking too much alcohol. Eat frequent, small meals (5 to 6 per day). Take care to eat sufficiently before exercising.
In addition to the above measures:
Wear a medical alert bracelet or other medical alert identification. Learn to recognize symptoms and take quick corrective measures.
American Diabetes Association website. Available at:
The Merck Manual of Medical Information—Home Edition
. Simon and Schuster, Inc; 2003.
The Merck Manual of Medical Information—Home Edition.
Simon and Schuster, Inc; 2000.
National Institute of Diabetes & Digestive & Kidney Diseases website. Available at:
Last reviewed January 2009 by
Rosalyn Carson-DeW¹itt, MD
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a
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