(Low Blood Glucose; Low Blood Sugar)



Glucose is a type of sugar. It is your body’s main source of energy. Hypoglycemia is a condition where the level of glucose in your blood becomes low enough to cause symptoms. When blood glucose drops too low, your body does not have enough energy to function properly.



Medications for diabetes are 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 thought to be rare.

Other causes of hypoglycemia include:

  • Alcohol use disorder, especially binge drinking coupled with not eating
  • Starvation
  • Early pregnancy
  • Certain pituitary or adrenal gland conditions
  • Certain liver conditions
  • Kidney disease
  • Certain types of stomach surgery
  • Tumor that makes insulin
  • Hereditary enzyme or hormone deficiencies
  • Severe illness or infection

Risk Factors

Risk Factors

Factors that may increase your chance of hypoglycemia include:

  • Having diabetes
  • Taking medications that lower blood sugar levels
  • Drinking too much alcohol
  • Fasting, particularly in combination with strenuous exercise



Symptoms may come on slowly or suddenly. Hypoglycemia may cause:

  • Sweating
  • Nervousness
  • Lightheadedness
  • Rapid heartbeat
  • Hunger
  • Headache
  • Tingling feeling around the mouth

As hypoglycemia worsens, it may cause:

  • Fatigue
  • Weakness
  • Inappropriate behavior or severe confusion
  • Poor control of movements
  • Seizure
  • Loss of consciousness

If you have frequent hypoglycemia, you may lose many of the early symptoms and be at particular risk of sudden loss of consciousness, seizure, or bizarre behavior. This could affect your ability to operate machinery or a motor vehicle. You will need to discuss any special instructions with your doctor.



You will be asked 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 you do not have diabetes, and you do not take medications that lower your blood sugar levels, other tests may be done to see if and why you are having low blood sugar levels. These tests may include checking your blood levels after periods of not eating.



Talk with your doctor about the best treatment plan for you. Options include:


Symptoms of low blood sugar can be relieved quickly by:

  • Eating sugar in a rapidly absorbable form, such as:

    • Fruit juice
    • Sugared soft drink
    • Table sugar in water
    • Honey or corn syrup
  • 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.


Some cases of hypoglycemia are caused by a tumor. In this case, the tumor may need to be removed.



To help reduce your chance of hypoglycemia:

  • For people with diabetes:

    • Monitor your medication. Take it as prescribed.
    • Follow the diet and exercise plans given by your doctor.
    • Avoid drinking alcohol in excess.
  • For non-diabetic people prone to hypoglycemia:

    • Avoid drinking too much alcohol.
    • Eat frequent, small meals.
    • Eat enough food before exercising.

If you are prone to severe hypoglycemia:

  • Wear a medical alert bracelet or other medical alert identification.
  • Learn to recognize symptoms and take quick corrective measures.


American Diabetes Association http://www.diabetes.org

Hypoglycemia Support Foundation http://www.hypoglycemia.org


Canadian Diabetes Association http://www.diabetes.ca

Health Canada http://www.hc-sc.gc.ca


Hypoglycemia. National Diabetes Information Clearinghouse website. Available at:
Updated November 6, 2012. Accessed September 30, 2014.

Hypoglycemia (low blood glucose). American Diabetes Association website. Available at:
Updated September 16, 2014. Accessed September 30, 2014.

Hypoglycemia in diabetes. EBSCO DynaMed website. Available at:
Updated September 29, 2014. Accessed September 30, 2014.

Hypoglycemia in persons without diabetes. EBSCO DynaMed website. Available at:
Updated September 29, 2014. Accessed September 30, 2014.

Last reviewed September 2015 by Kim Carmichael, MD
Last Updated: 9/30/2014

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