Low Blood Sugar (Hypoglycemia)

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Glucose is a type of sugar your body uses as a 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.

Causes of Hypoglycemia

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

Although rare, reactive hypoglycemia may also occur in people without diabetes.

Other causes of hypoglycemia include:

  • Alcohol abuse, 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

Are You at Risk?

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 and may cause:

  • Sweating
  • Nervousness
  • Lightheadedness
  • Heart palpitations
  • 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. 

Diagnosing Hypoglycemia

Your doctor will try to document your low blood sugar and measure your blood glucose levels while you're having symptoms.

If you don't have diabetes, and you don't take medications that lower your blood sugar levels, your doctor may do other tests to see if and why you're 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 that raises blood sugar levels.


Some cases are caused by a tumor, which may need to be removed.


To reduce your chance of hypoglycemia, take these steps:

  • 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.
  • 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.


Content was created using EBSCO’s Health Library. Edits to original content made by Rector and Visitors of the University of Virginia. This information is not a substitute for professional medical advice.