Hypoglycemia (Low Blood Sugar)


What is hypoglycemia?

Hypoglycemia is when the level of sugar in the blood drops below a healthy range. It’s also called low blood sugar or low blood glucose.

Everyone has different levels of blood sugar at different times. But for most people, low blood sugar is defined as below 70 mg/dL (milligrams per deciliter). Severe hypoglycemia usually happens at lower levels and is generally defined as a low blood sugar event that requires the assistance of someone else in order to correct the low blood sugar. Severe hypoglycemia is dangerous and needs treatment right away.

Symptoms and Causes

What causes hypoglycemia?

Hypoglycemia comes from too much insulin in the body. Insulin is a hormone that controls certain functions in your body. It helps your body use glucose for energy.

Hypoglycemia is most common, by far, in people with diabetes. Treatment for the disease often involves taking medication to increase insulin. Hypoglycemia can develop if things like food, exercise and diabetes medications are out of balance.

Common pitfalls for people with diabetes include:

  • Being more active than usual.
  • Drinking alcohol without eating.
  • Eating late or skipping meals.
  • Not balancing meals by including fat, protein and fiber.
  • Not eating enough carbohydrates.
  • Not timing insulin and carb intake correctly (for example, waiting too long to eat a meal after taking insulin for the meal).

Also, if someone with diabetes uses the wrong insulin, takes too much or injects it incorrectly, that can cause hypoglycemia.

Can someone have hypoglycemia without diabetes?

Very rarely, someone has hypoglycemia without diabetes. Scientists are still trying to understand the cause.

What are the symptoms of hypoglycemia?

Symptoms of hypoglycemia can start quickly, with people experiencing them in different ways. The signs of hypoglycemia are unpleasant. But they provide good warnings that you should take action before blood sugar drops more. The signs include:

  • Shaking or trembling.
  • Sweating and chills.
  • Dizziness or lightheadedness.
  • Faster heart rate.
  • Headaches.
  • Hunger.
  • Nausea.
  • Nervousness or irritability.
  • Pale skin.
  • Restless sleep.
  • Weakness.

You may also experience symptoms while sleeping:

  • Crying out loud.
  • Feeling tired or confused after waking up.
  • Having nightmares.
  • Sweating through pajamas or sheets.

When a hypoglycemic episode gets worse, the brain doesn’t get enough sugar, so you may experience:

  • Blurry vision.
  • Confusion or trouble concentrating.
  • Sleepiness.
  • Slurred speech.
  • Tingling or numbness in the face or mouth.

During a severe hypoglycemic event, a person may:

  • Be unable to eat or drink.
  • Have a seizure or convulsions (out-of-control body jerks).
  • Lose consciousness.
  • Slip into a coma or die (very rarely).

Does everyone have symptoms from hypoglycemia?

Some people don’t have symptoms or don’t notice them. Healthcare providers call that situation hypoglycemia unawareness. People with such a challenge aren’t aware when they need to do something about their blood sugar. They’re then more likely to have severe episodes and need medical help. People with hypoglycemia unawareness should check their blood sugar more often.

Diagnosis and Tests

How is hypoglycemia diagnosed?

The only way to know if you have hypoglycemia is to check your blood sugar with a blood glucose meter. It’s a small machine that measures blood sugar. Most of these devices use a tiny prick of the finger to take a small amount of blood.

People with hypoglycemia unawareness may need a continuous glucose monitor. These wearable devices measure glucose every few minutes, day and night. An alarm sounds if blood sugar drops too low.

Management and Treatment

How do I treat an episode of hypoglycemia?

The American Diabetes Association recommends the “15-15 rule” for an episode of hypoglycemia:

  • Eat or drink 15 grams of carbs to raise your blood sugar.
  • After 15 minutes, check your blood sugar.
  • If it’s still below 70 mg/dL, have another 15 grams of carbs.
  • Repeat until your blood sugar is at least 70 mg/dL.

If you have symptoms of hypoglycemia but can’t test your blood sugar, use the 15-15 rule until you feel better.

Note: Children need fewer grams of carbs. Check with your healthcare provider.

How do I measure carbs?

To know how many carbs you’re having, read food labels. Some examples of about 15 grams:

  • 1 small piece of fruit.
  • 1 tablespoon of sugar, honey or corn syrup.
  • 1 tube instant glucose gel (check the instructions).
  • 3 peppermint candies (not sugar-free).
  • 3-4 glucose tablets (check the instructions).
  • 4 ounces (half-cup) of juice or regular soda (not diet).
  • 5 Life Savers® candies (not sugar-free).

What if the 15-15 rule doesn’t work?

If you don’t feel better after three tries, or if your symptoms get worse, call your healthcare provider or 911. Healthcare providers can use a medication called glucagon. They inject it with a needle or squirt it up your nose. Glucagon is also available for home use. Your healthcare provider can prescribe it and teach a family member or friend how to use it in the event of severe hypoglycemia.


How can I prevent hypoglycemic episodes?

The key to preventing hypoglycemic events is managing diabetes:

  • Follow your healthcare provider’s instructions about food and exercise.
  • Track your blood sugar regularly, including before and after meals, before and after exercise and before bed.
  • Take all your medications exactly as prescribed.
  • When you do have a hypoglycemic event, write it down. Include details such as the time, what you ate recently, whether you exercised, the symptoms and your glucose level.

Outlook / Prognosis

What is the outlook for people with hypoglycemia?

Hypoglycemia can be managed when you and your healthcare provider understand what causes your blood sugar to go down. Give your healthcare provider as much information as possible about any hypoglycemic episodes. Fixing the problem may be as simple as changing the times you take medication, eat and exercise. Minor changes to the types of food you eat may also help.

Living With

How can I be better prepared for hypoglycemia?

You can take some steps to be ready for hypoglycemia:

  • Be aware of the symptoms and treat them early.
  • Carry some fast-acting carbs with you all the time.
  • Check your glucose levels frequently, especially around meals and exercise.
  • Inform family, friends and co-workers so they know what do if you need help.
  • Talk to your healthcare provider regularly to make and update your plan.
  • Wear a medical bracelet that lets people know you have diabetes. Carry a card in your purse or wallet with instructions for hypoglycemia.

A note from Cleveland Clinic

Hypoglycemia is quite common in people with diabetes. If not treated, it can cause troubling symptoms, and even serious health problems. Fortunately, you can avoid hypoglycemic episodes by monitoring your blood sugar. You can also make small adjustments to eating and exercising routines.

Last reviewed by a Cleveland Clinic medical professional on 03/25/2021.


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