What Is Hypoglycemia?

Hypoglycemia, also known as low blood sugar, occurs when the level of glucose (sugar) in your blood gets too low. Blood sugar levels naturally fluctuate throughout the day, and many people experience mild hypoglycemia now and then. However, severe hypoglycemia can be dangerous if not treated immediately.

Hypoglycemia is particularly common in people who have type 1 diabetes, as well as in people with type 2 diabetes who take insulin. Diabetes occurs when the pancreas makes little to no insulin, which is the hormone that helps balance your blood sugar levels. Hypoglycemia can also be caused by certain medical conditions or medications.

Symptoms of hypoglycemia range from hunger and shakiness to seizures and difficulty walking or talking, depending on the severity. Treatment focuses on raising blood glucose levels to within a normal range while determining the underlying cause helps inform prevention strategies.


Normal fasting blood glucose ranges from about 70 mg/dL to 99 mg/dL. Hypoglycemia ranges from mild (Level 1) to severe (Level 3):

  • Level 1: Blood glucose ranges from 54 milligrams per deciliter (mg/dL) to 70 mg/dL.
  • Level 2: Blood glucose falls below 54 mg/dL.
  • Level 3: Blood glucose is often below 40 mg/dL. This is severely low blood sugar that can limit your ability to function due to physical and/or mental changes.

Symptoms can happen quickly, and everyone's symptoms may be a little different. Early symptoms of hypoglycemia include hunger, shakiness, dizziness, sweating, and increased heart rate.

If these symptoms are not corrected or go unnoticed, they can progress into severe symptoms, including:

  • Confusion
  • Difficulty speaking
  • Difficulty walking
  • Fainting
  • Seizures

It's important to recognize what's happening in your body when your blood sugar dips so you can treat symptoms before they become severe.

What Causes Hypoglycemia?

Hypoglycemia occurs when the body uses up more glucose than it can make itself or obtain from food. This prohibits the body from releasing glucose into the bloodstream for energy and causes blood sugar to drop.

Glucose is the simplest form of sugar. Your body absorbs it from food and uses it for energy. Glucose fuels conscious processes, like coordinated movement and thinking, as well as unconscious processes, like breathing and cell repair.

Insulin and glucagon are hormones created by the pancreas. Together, they regulate blood sugar. In short, insulin prevents blood glucose from rising too high and glucagon prevents it from dropping too low. You can think of this blood-sugar regulating system like a thermostat: Its goal is to keep blood glucose within a specific range. Normal fasting blood glucose ranges from about 70 mg/dL to 99 mg/dL.

A variety of factors can cause hypoglycemia, and these factors vary based on what your hypoglycemia is caused by. 

Causes of Diabetic Hypoglycemia

Diabetes is a condition that affects the body's glucose-regulating system. People with type 1 diabetes don't make enough or any insulin. People with type 2 diabetes make insulin, but their bodies can't use it effectively. Low blood sugar is more common in people with type 1 diabetes, but it can also occur in people with type 2 diabetes. One 2016 global study of people with diabetes who take insulin found that 83% of people with type 1 diabetes and 46.5% of people with type 2 diabetes reported low blood sugar at least once over a four-week period.

Here are some causes of low blood glucose levels in people with either type 1 or type 2 diabetes:

  • Insulin: Taking too much insulin can cause blood glucose levels to drop.
  • Sulfonylureas and meglitinides: These are classes of diabetes medications that can lower blood glucose levels.
  • Carbohydrates: The carbohydrates you eat provide your body with glucose. Not eating enough carbohydrates can result in low glucose levels. The ideal amount varies from person to person, depending on factors like age and activity level. Still, it’s helpful to aim for similar grams of carbohydrates with each meal to keep blood sugar balanced.
  • Fasting: Fasting can increase your risk of hypoglycemia, particularly if you're taking medication to lower your blood glucose.
  • Physical activity: Exercising lowers glucose levels, which is usually beneficial for people with diabetes. However, exercising beyond your normal workout routine can lower blood glucose for up to 24 hours post-exercise.
  • Alcohol: Drinking alcohol without eating enough food can make it harder for your body to maintain normal blood glucose levels. Plus, you might not feel the early symptoms of hypoglycemia if you've been drinking.
  • Illness: Illness may affect how much you're able to eat, which can lower blood glucose.

Causes of Nondiabetic Hypoglycemia

Hypoglycemia that is not related to diabetes is rare, but it can happen. For example, people 65 years and older may be at higher risk of developing this type of hypoglycemia.

People with other insulin-related conditions may also develop hypoglycemia. Insulinoma (a tumor in the pancreas) and non-insulinoma pancreatogenous hypoglycemia syndrome (NIPH) are rare conditions that can cause hypoglycemia. Insulin autoimmune hypoglycemia may also increase your of low blood glucose.

Other causes of nondiabetic hypoglycemia that don't involve insulin include:

  • Alcohol, especially on an empty stomach
  • Liver/kidney failure
  • Critical illness, for example, because the body can use more glucose when under severe stress
  • Primary adrenal failure, also called Addison’s disease, which is when the adrenal glands on top of the kidneys don’t produce enough hormones
  • Anterior pituitary failure, also called hypopituitarism, which is when the pituitary gland in the brain doesn’t produce enough hormones
  • Severe sepsis, which is when the body has a dangerously overactive response to an infection
  • Anorexia, an eating disorder that causes someone to eat either nothing or very little
  • Glycogen storage disease, a rare metabolic disorder
  • Complications following bariatric surgery, a type of weight loss surgery
  • Tumors of the connective tissue, blood vessels, and lymphatic tissue

Drugs are also a common cause of hypoglycemia. Drugs that have been reported to lower blood sugar include:

  • Quinolones: Bactericidal antibiotics used to kill bacterial cells
  • Anti-malarial drugs: Drugs used to treat malaria, a parasitic disease that is passed through mosquito bites
  • Glucagon: A medication used to treat severe low blood sugar that can actually lower blood sugar in people who have insulinoma or pheochromacytoma (a tumor in the adrenal gland)    
  • Lithium: A medication used to treat mood disorders 
  • Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor antagonists: Classes of medications used to lower blood pressure
  • Non-selective beta-blockers: A class of medications used to treat heart disease 

How Is Hypoglycemia Diagnosed?

Testing is the only way to confirm hypoglycemia. You need to test when you're having symptoms or after you've been fasting for 72 hours.

People with diabetes often have a blood monitoring device at home, such as a blood glucose monitor (also called a glucometer), so they can check their blood sugar regularly. Blood tests can also diagnose hypoglycemia. Common blood tests include blood glucose tests, which measure the amount of glucose in your blood.

Healthcare providers will try to pinpoint the underlying cause for low blood sugar—including diabetes, kidney injury or kidney failure, or hormone deficiencies. This might include additional testing. For example, a C-peptide blood test, which assesses how much insulin your body produces, can help determine high insulin levels.

Healthcare providers will also want to know information about potential factors like the following:

  • The onset of symptoms in relation to meals and exercise
  • Current medications
  • Alcohol or drug use
  • If diabetes or other endocrine disorders run in your family


The first goal of treatment is to return blood sugar levels to normal. This ensures that your blood contains adequate energy for organ, tissue, and cell function. Once glucose levels are within the normal range, the goal is to treat the underlying cause.

Symptoms need to be treated right away. If you can't test your blood glucose for whatever reason, treat your hypoglycemia.

In people with diabetes, the immediate fix is sometimes called the 15-15 Rule or the Rule of 15s: Eat 15 grams of carbohydrates to raise your blood glucose levels, then wait 15 minutes to test. If your levels are still below 70 mg/dL, eat another 15 grams of carbohydrates and test again 15 minutes later. Repeat these steps until your blood sugar is at least at 70 mg/dL.

After that, have a small snack to keep your glucose levels up. The American Diabetes Association recommends the following options:

  • Glucose tablets (follow the instructions on the package)
  • Gel tube (follow the instructions on the package)
  • Four ounces (one-half cup) of juice or regular soda (not diet soda)
  • One tablespoon of sugar, honey, or corn syrup
  • Hard candies, jellybeans, or gumdrops (see the label for how many to consume)

The type of carbohydrate matters. If you're trying to raise your blood sugar level, avoid complex carbohydrates like wheat bread, pasta, rice, starchy vegetables, and legumes, as well as carbohydrates that contain fats, including chocolate.

Talk to a healthcare provider after your symptoms resolve.

Treatments for Severe Hypoglycemia

Hypoglycemia is considered severe when low blood glucose reaches the point where you need help from another person to recover. To avoid reaching this point, people with diabetes may have a glucagon prescription from a healthcare provider.

If you have diabetes, make sure the people you see frequently (friends, family, coworkers, etc.) know where your glucagon is and how to give it to you if you need it.

Here are some recommendations for treating severe hypoglycemia:

  • Administer glucagon if it's available. Know that it might take a person with severe hypoglycemia about five to 15 minutes to regain consciousness, at which point they might be nauseous and vomit.
  • Call 911 if you need help. If someone is unconscious and you don't have glucagon or don't know how to use it, get medical help immediately.
  • If a person with diabetes is experiencing hypoglycemia, do not give that person insulin. Insulin will cause blood glucose to drop even more.
  • Do not give food or fluid to a person who is unconscious, as this could cause choking.

How to Prevent Hypoglycemia

Preventing hypoglycemia depends on the underlying cause. Pay attention to how eating and exercise habits, as well as medications, might impact your symptoms. Try eating smaller meals and snacks every few hours or so throughout the day. You may also want to avoid foods high in sugar, alcohol, and caffeine. In addition, talk to a healthcare provider about treating the underlying cause.

If you have diabetes, you can prevent hypoglycemia by managing your diabetes. This includes being vigilant about testing your blood sugar and developing eating habits that help regulate your blood sugar. Wearing a continuous glucose monitoring (CGM) device may also help. These devices allow you to see where your levels are before they get too low.

Learning how to detect hypoglycemia early can help prevent blood glucose from dropping to dangerous levels.

Comorbid Conditions

Research on hypoglycemia often focuses on people with type 2 diabetes. For example, people with diabetes who are at greater risk of hypoglycemia might also be diagnosed with conditions like hypertension, heart disease, cancer, renal (kidney) disease, and liver cirrhosis. Other potential risk factors for hypoglycemia include endocrine disorders and low body mass index (BMI).

Repeated episodes of hypoglycemia may put you at risk of developing hypoglycemia unawareness: not noticing symptoms of low blood sugar until your blood sugar is dangerously low. Keep close tabs on your blood glucose levels by testing often. This will help you prevent additional complications of low blood sugar.

Talk to a healthcare provider for guidance on how you can prevent hypoglycemia from happening based on your individual needs and concerns.

Living With the Risk of Hypoglycemia

Hypoglycemia is very treatable and often preventable with lifestyle modifications such as keeping shelf-stable snacks easily accessible. Staying mindful with diet and exercise can help you keep your blood sugar levels in check, especially if you have diabetes.

Whether or not you have diabetes, you may also want to talk to your healthcare provider to see if a medication you're taking is interfering with your blood sugar levels. You may be able to switch to a different medication.

Living with the risk of hypoglycemia may require extra effort initially, but it will get easier over time. Check your blood sugar regularly and pay close attention to how your body feels when your blood sugar gets low. Knowing how it feels can help you take preventive measures.

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Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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