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Patient education: Hypoglycemia (low blood glucose) in people with diabetes (Beyond the Basics)

Patient education: Hypoglycemia (low blood glucose) in people with diabetes (Beyond the Basics)
Kasia J Lipska, MD, MHS
Section Editor:
David M Nathan, MD
Deputy Editor:
Katya Rubinow, MD
Literature review current through: Nov 2022. | This topic last updated: Aug 25, 2021.

INTRODUCTION — Hypoglycemia is the medical term for low blood glucose (blood sugar). People with type 1 diabetes who need to take insulin to control their blood glucose levels are at risk for getting hypoglycemia. People with type 2 diabetes who take insulin and/or certain other medications (eg, sulfonylureas, meglitinides) can also develop hypoglycemia, although this is generally less common. The frequency of hypoglycemia among people with longstanding type 2 diabetes increases over time, as the body eventually stops making enough insulin.

HYPOGLYCEMIA CAUSES — Low blood glucose can happen if you:

Take too much insulin

Take too much of oral diabetes medications that cause your body to release more insulin (eg, sulfonylureas, meglitinides)

Do not eat enough food

Exercise vigorously without eating a snack or decreasing your insulin dose beforehand

Wait too long between meals

Drink a lot of alcohol

HYPOGLYCEMIA SYMPTOMS — The symptoms of low blood glucose vary from person to person and can change over time. During the early stages of low blood glucose, you may:



Feel hungry

Feel anxious

If untreated, symptoms can become more severe and can include:

Difficulty walking


Difficulty seeing clearly

Bizarre behavior or personality changes


Passing out or having a seizure

When possible, you should confirm that you have hypoglycemia by measuring your blood glucose level (see "Patient education: Blood glucose monitoring in diabetes (Beyond the Basics)"). A glucose level of ≤70 mg/dL (3.9 mmol/L) indicates the possibility of developing more serious hypoglycemia. Action may be needed to prevent the glucose from getting even lower. Serious hypoglycemia is generally defined as a blood glucose below 54 mg/dL (3 mmol/L). This level of hypoglycemia should be immediately treated. Severe hypoglycemia is defined as an event during which you are confused or pass out and need the help of another person for recovery, regardless of your glucose level. (See 'Hypoglycemia treatment' below.)

Some people with diabetes develop symptoms of low blood glucose at slightly higher levels. If your blood glucose levels are high for long periods of time, you may notice symptoms before your blood glucose gets below 70 mg/dL. Getting your blood glucose under better control can help to lower the blood glucose level when you begin to feel symptoms.

Hypoglycemia unawareness — Hypoglycemia unawareness is when you do not have the early symptoms of low blood glucose. Being unaware of low blood glucose is a common occurrence, especially in people who have had type 1 diabetes for more than 5 to 10 years, but it can be dangerous. When you have hypoglycemia unawareness, you cannot respond in the early stages, and severe signs of low blood glucose (such as passing out or seizures) are more likely.

Hypoglycemia unawareness can result from recurrent episodes of hypoglycemia, particularly when those episodes are serious (glucose below 54 mg/dL). Hypoglycemia and hypoglycemia unawareness occur more frequently in people who tightly control their blood glucose levels with insulin (called intensive therapy). (See "Patient education: Type 1 diabetes: Insulin treatment (Beyond the Basics)", section on 'Intensive insulin treatment'.)

People who are under the influence of alcohol, are tired, or take a beta blocker (a medication commonly used to control high blood pressure) may not notice early low blood glucose symptoms, or may not recognize that the symptoms are due to low blood glucose.

Nocturnal hypoglycemia — Low blood glucose that occurs when you are sleeping (called nocturnal hypoglycemia) can disrupt sleep but often goes unrecognized. Nocturnal hypoglycemia is a form of hypoglycemia unawareness. Thus, if you have nocturnal hypoglycemia, you are less likely to have symptoms that alert you to the need for treatment. Nocturnal hypoglycemia can be difficult to diagnose and can increase the risk of hypoglycemia unawareness in the 48 to 72 hours that follow.

HYPOGLYCEMIA PREVENTION — To prevent low blood glucose, it is important to monitor your blood glucose levels frequently and be prepared to treat it promptly at any time. You and a close friend or relative should learn the symptoms and always carry glucose tablets, hard candy, or other sources of fast-acting carbohydrate so you can treat low blood glucose if it does happen. (See 'Hypoglycemia treatment' below.)

Glucose tablets are recommended since they have a pleasant taste, but you are not likely to eat them unless your blood glucose is low. Candy can be tempting to eat, even when blood glucose levels are normal, especially for children with diabetes.

If you experience low blood glucose levels, let your health care provider know. They can help adjust your diabetes treatment plan to reduce the chances of hypoglycemia happening again. They can also talk to you about blood glucose awareness education. Blood glucose awareness training can improve your ability to recognize low blood glucose earlier, which will allow you to treat it quickly and avoid more serious symptoms. A trained diabetes educator can also work with you to help you anticipate when low glucose levels are more likely to happen.

Low blood glucose can be frightening and unpleasant. If you have experienced this before, you may be worried or anxious about the possibility of it happening again. However, it's important to talk to your health care provider and not just intentionally keep your blood glucose high because of this. High blood glucose levels can lead to serious long-term complications. (See "Patient education: Preventing complications from diabetes (Beyond the Basics)".)

HYPOGLYCEMIA TREATMENT — The treatment of low blood glucose depends on whether you have symptoms and how severe the symptoms are.

No symptoms — Your health care provider will talk to you about what to do if you check your blood glucose and it is low, but you have no noticeable symptoms. They might recommend checking your levels again after a short time, avoiding activities like driving, or eating something with carbohydrates.

Early symptoms — If you have early symptoms of low blood glucose, you should check your level as soon as possible. However, if your monitoring equipment is not readily available, you can go ahead and give yourself treatment. It's important to treat low blood glucose as soon as possible.

To treat low blood glucose, eat 15 to 20 grams of fast-acting carbohydrate. You can do this by eating 3 or 4 glucose tablets or 6 to 8 hard candies, or drinking 1/2 cup of fruit juice.

This amount of food is usually enough to raise your blood glucose into a safe range without causing it to get too high. Avoid foods that contain fat (like candy bars) or protein (such as cheese) initially, since they slow down your body's ability to absorb glucose.

Check your blood glucose again after 15 minutes and repeat treatment if your level is still low. Monitor your blood glucose levels more frequently for the next few hours to ensure your blood glucose levels are not low.

Severe symptoms — If your blood glucose is very low, you may pass out or become too disoriented to eat. A close friend or relative should be trained to recognize severe low blood glucose and treat it quickly. Dealing with a loved one who is pale, sweaty, acting bizarrely, or is passed out and convulsing can be scary. A dose of glucagon stops these symptoms quickly.

Glucagon is a hormone that raises blood glucose levels. Glucagon is available in emergency kits (as an injection or a nasal spray), which can be bought with a prescription in a pharmacy. Directions are included in each kit; a roommate, partner, parent, or friend should learn how to give glucagon before an emergency occurs.

It is important that your glucagon kit is easy to locate, is not expired, and that the friend or relative is able to stay calm. You should refill the kit when the expiration date approaches, although using an expired kit is unlikely to cause harm.

Glucagon is available as an injection (shot) or as a nasal spray:

Injectable glucagon – This comes in a prefilled syringe or an autoinjector "pen" (figure 1) The shot should be given in the upper arm, thigh, or abdomen.

Nasal spray – Nasal glucagon is given by placing the tip of the device in one nostril and pushing a small plunger. This releases the powder into the person's nostril without requiring them to inhale or do anything else.

If you have to give another person glucagon, turn them onto their side afterwards. This prevents choking if they vomit, which sometimes happens.

Low blood glucose symptoms should resolve within 10 to 15 minutes after a dose of glucagon, although nausea and vomiting may follow 60 to 90 minutes later. As soon as the person is awake and able to swallow, offer a fast-acting carbohydrate such as glucose tablets or juice.

If the person is not conscious within approximately 15 minutes, call for emergency help (in the United States and Canada, dial 9-1-1) and give the person another dose of glucagon, if a second kit is available.

FOLLOW-UP CARE — After your blood glucose level normalizes and your symptoms are gone, you can usually resume your normal activities. If you required glucagon, you should call your health care provider right away. They can help you to determine how and why you developed severely low blood glucose and can suggest adjustments to prevent future reactions.

In the first 48 to 72 hours after a low blood glucose episode, you may have difficulty recognizing the symptoms of low blood glucose. In addition, your body's ability to counteract low blood glucose levels is decreased. Check your blood glucose level before you eat, exercise, or drive to avoid another low blood glucose episode.

WHEN TO SEEK HELP — A family member or friend should take you to the hospital or call for emergency assistance immediately if you:

Remain confused 15 minutes after being treated with glucagon

Are unconscious (or nearly unconscious) and glucagon is not available

Continue to have low blood glucose despite treatment with a fast-acting carbohydrate or glucagon

Once in a hospital or ambulance, you will be given treatment intravenously (by IV) to raise your blood glucose level immediately. If you require emergency care, you may be observed in the emergency department for a few hours before being released. In this situation, you will need someone else to drive you home.

WHERE TO GET MORE INFORMATION — Your health care provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our website ( Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Type 1 diabetes (The Basics)
Patient education: Low blood sugar in people with diabetes (The Basics)
Patient education: Diabetes and diet (The Basics)
Patient education: Should I switch to an insulin pump? (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Type 1 diabetes: Insulin treatment (Beyond the Basics)
Patient education: Type 1 diabetes: Overview (Beyond the Basics)
Patient education: Type 2 diabetes: Alcohol, exercise, and medical care (Beyond the Basics)
Patient education: Type 2 diabetes: Overview (Beyond the Basics)
Patient education: Type 2 diabetes: Treatment (Beyond the Basics)
Patient education: Preventing complications from diabetes (Beyond the Basics)
Patient education: Blood glucose monitoring in diabetes (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Hypoglycemia in adults without diabetes mellitus: Diagnostic approach
Diagnostic dilemmas in hypoglycemia: Illustrative cases
Factitious hypoglycemia
Management of blood glucose in adults with type 1 diabetes mellitus
Insulin therapy in type 2 diabetes mellitus
Insulin-induced hypoglycemia test
Hypoglycemia in adults with diabetes mellitus
Hypoglycemia in adults without diabetes mellitus: Clinical manifestations, diagnosis, and causes
Physiologic response to hypoglycemia in healthy individuals and patients with diabetes mellitus
Evaluation of postprandial symptoms of hypoglycemia in adults without diabetes

The following organizations also provide reliable health information.

National Library of Medicine


National Institute of Diabetes & Digestive & Kidney Diseases


American Diabetes Association (ADA)

(800)-DIABETES (800-342-2383)


The Endocrine Society


Hormone Health Network



This generalized information is a limited summary of diagnosis, treatment, and/or medication information. It is not meant to be comprehensive and should be used as a tool to help the user understand and/or assess potential diagnostic and treatment options. It does NOT include all information about conditions, treatments, medications, side effects, or risks that may apply to a specific patient. It is not intended to be medical advice or a substitute for the medical advice, diagnosis, or treatment of a health care provider based on the health care provider's examination and assessment of a patient's specific and unique circumstances. Patients must speak with a health care provider for complete information about their health, medical questions, and treatment options, including any risks or benefits regarding use of medications. This information does not endorse any treatments or medications as safe, effective, or approved for treating a specific patient. UpToDate, Inc. and its affiliates disclaim any warranty or liability relating to this information or the use thereof. The use of this information is governed by the Terms of Use, available at ©2023 UpToDate, Inc. and its affiliates and/or licensors. All rights reserved.
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