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(Low Blood Sugar)

En Español (Spanish Version)


Hypoglycemia is a condition where the level of glucose in the blood stream becomes too low. Glucose, a type of sugar (carbohydrate), is the body's main source of fuel. When the level of glucose in the blood stream falls too low, the body is without sufficient fuel to function properly.

Glucose in Blood

glucose and RBC

© 2008 Nucleus Medical Art, Inc.


Hypoglycemia most often occurs in people treated with medication for diabetes . It can result from a combination of 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

Diabetic patients must consistently find a balance between the benefits of tight glucose control and the risk of hypoglycemia.

Hypoglycemia may also occur in certain predisposed individuals without diabetes. Reactive hypoglycemia, once a popular diagnosis, 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:

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.


Symptoms may come on slowly or suddenly.

Symptoms include:

  • 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, and perform a physical exam. Initial diagnosis is based on your symptoms. If hypoglycemia is suspected, your doctor will try to document your low blood sugar by measuring your blood glucose level while you are having symptoms. If this is not possible, you may have a glucose tolerance test. This involves a series of blood tests after taking glucose orally.

Other, less routine tests include:

  • Laboratory tests for antibodies to insulin
  • Imaging tests to check for a tumor, such as:
    • MRI scan—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


Treatments include:


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
  • Intravenous glucose (in severe cases)


Some people who have prolonged or severe hypoglycemia take glucagon. Glucagon is an injectable hormone that raises blood sugar levels. It can be used in emergencies when people with diabetes have a hypoglycemic reaction and cannot take sugar by mouth.


If hypoglycemia is caused by a tumor, surgery to remove the tumor may be necessary.


Measures that can help prevent hypoglycemia include:

People With Diabetes

  • Closely monitor medication as prescribed by your doctor.
  • Closely follow diet and exercise regimen prescribed by your doctor.
  • Avoid drinking alcohol in excess.

Non-Diabetic People Prone to Hypoglycemia

  • Avoid drinking too much alcohol.
  • Eat frequent, small meals (5 to 6 per day).
  • Take care to eat sufficiently before exercising.

People Prone to Severe Hypoglycemia

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

Hypoglycemia Support Foundation


Canadian Diabetes Association

Canadian Health Network


American Diabetes Association website. Available at: http://www.diabetes.org .

Beers MH. 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: http://www2.niddk.nih.gov/ .

Last reviewed October 2007 by Rosalyn Carson-DeWitt, 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 medical condition.

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