Merck Manual

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Quick Facts



The Manual's Editorial Staff

Last full review/revision May 2021| Content last modified May 2021
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What is hypoglycemia?

"Hypo" means low. "Glycemia" has to do with the amount of sugar (glucose) in your blood (blood sugar). So, hypoglycemia is when your blood sugar drops too low. Blood sugar is your body's main source of fuel, so low blood sugar causes problems.

  • Hypoglycemia causes hunger, sweating, shakiness, and weakness, and makes it hard to think clearly

  • If you have diabetes, you're more likely to get hypoglycemia—it can happen if you take too much medicine, don’t eat enough, or exercise too much

  • To treat hypoglycemia, eat or drink something with sugar (like juice or candy) to raise your blood sugar level

What causes hypoglycemia?

Most often, hypoglycemia is:

If you don't have diabetes, you're not likely to get hypoglycemia. However, sometimes you may get hypoglycemia if you:

What are the symptoms of hypoglycemia?

At first, you may have these symptoms:

  • Sweating

  • Shaking

  • Feeling lightheaded

  • Hunger

Later, if you have severe hypoglycemia, you may have these symptoms:

  • Dizziness

  • Confusion and trouble concentrating

  • Slurred speech

  • Passing out

Sometimes, hypoglycemia makes it seem like you're drunk.

How can doctors tell if I have hypoglycemia?

Doctors diagnose hypoglycemia based on your blood sugar level while you're actually having symptoms.

How do doctors treat hypoglycemia?

Doctors will tell you to treat your symptoms at home. If you're having symptoms, eat or drink sugar, such as:

  • Candy

  • Glucose (sugar) tablets

  • Sugary drink, such as a glass of fruit juice

Doctors will treat the cause of your hypoglycemia:

  • If a medicine is causing hypoglycemia, doctors will change the amount you take

  • If you have a tumor in your pancreas, doctors will do surgery to take it out

If you have diabetes or are otherwise at risk for hypoglycemia, your doctor may suggest you:

  • Keep glucagon with you in case of an emergency (glucagon is a shot that raises your blood sugar level quickly)

  • Eat small meals throughout the day instead of 3 large meals

  • Limit the carbohydrates you eat

  • Carry or wear a medical ID to let other doctors know you have diabetes in case of a medical emergency

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