Hypoglycemia

Low blood sugar can cause symptoms that aren't comfortable, such as dizziness and confusion. The condition can quickly become serious if not treated.

Update Date: 05.09.2026

Overview
Symptoms
Causes
Risk factors
Complications
Causes
Prevention
Diagnosis
Treatment
Preparing for an appointment

Overview

Hypoglycemia is a condition caused by low blood sugar, also called blood glucose. Glucose is your body's main energy source.

Hypoglycemia is often related to diabetes treatment. But other medicines and conditions, many of them rare, can cause low blood sugar in people who don't have diabetes.

For many people, a fasting blood sugar of 70 milligrams per deciliter (mg/dL), which is 3.9 millimoles per liter (mmol/L), or below is usually an alert for hypoglycemia. But your numbers might be different. Talk with your healthcare professional about what's right for you.

Hypoglycemia needs treatment right away. The goal of treatment is to quickly get your blood sugar back to within the standard range. This is done either with a high-sugar food or drink or with medicine. Long-term treatment involves finding the cause of hypoglycemia and treating it.

Symptoms

Hypoglycemia can include these warning symptoms:

  • Blue or gray skin.
  • Shakiness.
  • Sweating.
  • Headache.
  • Hunger or upset stomach, also called nausea.
  • Heartbeat that's fast or isn't regular.
  • Feeling tired or weak.
  • Feeling irritable or anxious.
  • Trouble thinking or paying attention.
  • Dizziness or lightheadedness.
  • Tingling or numbness of the lips, tongue or cheek.

As hypoglycemia worsens, symptoms can be more severe and include:

  • Confusion, behavior that is not usual or both, such as not being able to do routine tasks.
  • Loss of coordination, such as trouble walking.
  • Slurred speech.
  • Blurry vision or tunnel vision.
  • Double vision.
  • Nightmares, if asleep.

Severe hypoglycemia may cause:

  • Not being able to respond or help oneself.
  • Fainting or losing consciousness.
  • Seizures.
  • Coma, rarely.

When to see a doctor

Seek medical help right away if:

  • You have what might be hypoglycemia symptoms and you don't have diabetes.
  • You have diabetes, and hypoglycemia isn't getting better with treatment, such as drinking juice or regular, not diet, soft drinks; eating candy; or taking glucose tablets.
  • You have diabetes, and hypoglycemia happens again even though you just treated it with a fast-acting carbohydrate, such as juice, a regular soft drink, candy or glucose tablets.

Get emergency help for someone with diabetes or a history of hypoglycemia who has symptoms of severe hypoglycemia or loses consciousness.

Causes

Hypoglycemia happens when your blood sugar level, also called blood glucose level, falls too low for the body to function. There are several reasons why this can happen. The most common reason for low blood sugar is a side effect of medicines used to treat diabetes.

Blood sugar balance

When you eat, your body breaks down foods into glucose. Glucose, the main energy source for the body, enters the cells with the help of insulin. Insulin is a hormone made by the pancreas. Insulin allows glucose to enter cells and give them the fuel the body needs. Extra glucose is stored in the liver and muscles in the form of glycogen.

When you haven't eaten for many hours and your blood sugar level drops, you stop making insulin. Another hormone from the pancreas called glucagon signals the liver to break down the stored glycogen into glucose. The glucose is released into the bloodstream. This keeps your blood sugar within the standard range until you eat again.

Your body also can make glucose. This process happens mainly in the liver but also in the kidneys. With long periods of fasting, the body can break down protein and fat stores and make new glucose. Products of fat breakdown can be used as another fuel source.

Possible causes, with diabetes

If you have diabetes, your body might not make insulin. This happens in type 1 diabetes. Or your body might make less insulin than what it needs. This happens in type 2 diabetes. As a result, glucose builds up in the bloodstream and can reach dangerously high levels. To lower these levels, you might take insulin or other medicines.

But too much insulin or other diabetes medicine may cause your blood sugar level to drop too much. This results in hypoglycemia. Hypoglycemia also can happen if you eat less than usual after taking your regular dose of diabetes medicine, or if you exercise more than you typically do.

Possible causes, without diabetes

Hypoglycemia in people without diabetes is much less common. Causes can include:

  • Medicines. Taking someone else's diabetes medicine is a possible cause of hypoglycemia. Other medicines can cause hypoglycemia, especially in children or in people with kidney failure. One example is quinine, used to treat malaria.
  • Drinking too much alcohol. Drinking heavily without eating can keep the liver from making new glucose and releasing it into the bloodstream. This can lead to hypoglycemia.
  • Some serious medical conditions. Severe liver conditions such as liver failure, severe hepatitis or cirrhosis, severe infection, and advanced kidney disease can cause hypoglycemia. Kidney conditions also can keep your body from getting rid of medicines as it should. This can affect glucose levels due to a buildup of medicines that lower blood sugar levels.
  • Long-term starvation. Low blood sugar occurs with malnutrition and starvation. When you don't get enough food, the glycogen your body stores to make glucose is used up. This can happen in people with advanced heart failure, advanced cancer and an eating disorder called anorexia nervosa.
  • Making too much insulin. A rare tumor of the pancreas called insulinoma can cause the body to make too much insulin. This can cause hypoglycemia. Other tumors also can lead to the body making too much of insulinlike substances.
  • Not having enough of certain hormones. Certain adrenal gland and pituitary tumor conditions can happen due to the body not having enough of certain hormones that balance how much glucose is made. Children can have hypoglycemia if they have too little growth hormone.

Hypoglycemia after meals

Sometimes hypoglycemia symptoms happen after certain meals. The cause is low sugar from a mismatch between food and insulin released in response to food.

Hypoglycemia that happens after eating is called postprandial hypoglycemia. This type happens often in people who've had surgeries that change the usual way the stomach works. The surgery most commonly linked to this is stomach bypass surgery, also called bariatric surgery. But postprandial hypoglycemia also can happen in people who've had other surgeries or who haven't had any surgery.

About 1 in 10 healthy people has glucose levels less than 70 mg/dL after drinking sugar-containing drinks and does not have symptoms of hypoglycemia.

Risk factors

The most common risk factor for hypoglycemia is having diabetes and taking insulin or some of the other diabetes medicines.

Risk factors for people without diabetes include not eating enough, drinking too much alcohol, taking certain medicines or having certain medical conditions that change how the body manages insulin and glucose.

Complications

Hypoglycemia that isn't treated can lead to:

  • Seizure.
  • Coma.
  • Heartbeat that is too fast or isn't regular.
  • Death.

Hypoglycemia also can cause:

  • Dizziness and weakness.
  • Falls.
  • Injuries.
  • Motor vehicle accidents.
  • Greater risk of dementia in older adults.

Causes

Impaired hypoglycemia awareness

Over time, having repeated hypoglycemia can lead to serious effects of hypoglycemia without the warning symptoms. Impaired hypoglycemia awareness is sometimes also called hypoglycemia unawareness. The body and brain no longer show the symptoms that warn of low blood sugar, such as shakiness or heartbeats that aren't regular. When this happens, the risk of severe, life-threatening hypoglycemia goes up.

If you have diabetes and often have hypoglycemia along with impaired hypoglycemia awareness, your healthcare professional might change your treatment, raise your blood sugar level goals and recommend blood glucose awareness training.

A continuous glucose monitor (CGM) is an option for some people with diabetes and impaired hypoglycemia awareness. A CGM can warn you if your blood glucose level is dropping too low so you can manage it to prevent hypoglycemia. A CGM also can alert you when your blood glucose is dangerously low.

Undertreated diabetes

If you have diabetes, periods of low blood sugar are not comfortable and can be frightening. Fear of hypoglycemia can cause you to take less insulin to make sure that your blood sugar level doesn't go too low. This can lead to diabetes that isn't well controlled. Talk with your healthcare professional about your fear. Some people with diabetes have had training to adjust their treatment themselves. If you have not had this training, don't change your diabetes medicine dose without talking with your healthcare professional.

Prevention

If you have diabetes

Follow the diabetes management plan you and your healthcare professional have made. If you're taking new medicines, changing your eating or medicine schedules, or adding new exercise, talk with your healthcare professional about how these changes might affect your diabetes management and your risk of low blood sugar.

Learn the symptoms you have with low blood sugar. This can help you be aware of and treat hypoglycemia before your blood sugar level gets too low. Checking your blood sugar level often lets you know when your blood sugar is getting low and what might cause it. You might choose to let family and friends know your low blood sugar symptoms so they can watch for them too.

A continuous glucose monitor is a good option for some people. A CGM has a tiny wire that's inserted under the skin. The wire sends blood glucose readings to a receiver. If your blood sugar level is dropping too low, some CGM models alert you with an alarm.

Some insulin pumps are linked to CGMs. Insulin pumps are programmed to deliver insulin continuously, with food or as needed. The pumps can lower and even shut off insulin delivery when blood sugar levels are dropping too fast. This can help keep hypoglycemia from happening.

Be sure to always have a fast-acting carbohydrate with you, such as juice, hard candy or glucose tablets. Then you can treat a falling blood sugar level before it gets dangerously low.

If you don't have diabetes

Eating often can prevent hypoglycemia in some people who have the condition when not eating. Eating food containing complex starch, such as whole grains, legumes and starchy vegetables, can help keep glucose levels steady and prevent hypoglycemia in some people.

Eating smaller meals can prevent hypoglycemia in some people with postprandial hypoglycemia. Changing the type of food you eat also may be helpful, such as not having foods and drinks that have a lot of sugar.

Work with your healthcare professional to find and treat the cause of your hypoglycemia.

Continuous glucose monitor and insulin pump

A continuous glucose monitor, on the left, is a device that measures blood sugar every few minutes using a sensor placed under the skin. An insulin pump, attached to the pocket, is a device that's worn outside of the body. A tube connects the reservoir of insulin to a catheter placed under the skin of the belly.

Diagnosis

If you have hypoglycemia symptoms, your healthcare professional does a physical exam and reviews your medical history. You'll likely have a blood test to check your blood glucose level. Your healthcare professional also may order other blood tests to look for causes of hypoglycemia.

If you use insulin or another diabetes medicine to lower your blood sugar and you have symptoms of hypoglycemia, test your blood sugar level with a blood glucose meter. If the result shows low blood sugar, under 70 mg/dL (3.9 mmol/L), treat it based on your diabetes treatment plan. If you can't check your blood sugar, it may be OK to treat symptoms of hypoglycemia anyway.

Keep a record of your blood sugar testing results and how you have treated low blood sugar levels. Your healthcare professional can review the information to help change your diabetes treatment plan if needed.

In a person not taking medicines for diabetes, hypoglycemia is diagnosed using a guideline called the Whipple triad. To diagnose hypoglycemia, this guideline requires that a person has:

  • Symptoms of hypoglycemia.
  • A laboratory blood test result showing low plasma glucose.
  • Relief of hypoglycemia symptoms when low plasma glucose is corrected.

If you don't use medicines known to cause hypoglycemia, your healthcare professional will likely ask:

  • What were your symptoms? If you don't have symptoms of hypoglycemia during your visit, your healthcare professional might have you not eat, called fasting, overnight or longer. This allows low blood sugar symptoms to happen and can help your healthcare professional make a diagnosis. Another option is an extended fast that's up to 72 hours. This is usually done in a hospital.
  • What is your blood sugar level when you're having symptoms? A healthcare professional takes a blood sample and sends it to a lab. If your symptoms happen after a meal, the blood sugar test may be done after you eat. Another option is to have a monitored mixed meal test to see how your blood sugar reacts to certain foods.
  • Do your symptoms go away when you eat fast-acting carbohydrates to raise your blood sugar levels? This helps your health professional know whether your symptoms are caused by low blood sugar.
  • Did your symptoms happen after an overnight fast or after eating something? If your symptoms happen after eating, what did you eat?

Treatment

How to treat hypoglycemia right away

If you have hypoglycemia symptoms, do the following:

  • Eat or drink about 15 grams of fast-acting carbohydrates. These are sugary foods or drinks without protein or fat that are easily made into sugar in the body. Try glucose tablets or gel; fruit juice; regular, not diet, soda; honey; or sugary candy. Always carry with you fast-acting carbohydrates to treat low blood sugar.
  • Recheck your blood sugar level 15 minutes after treatment. If the blood sugar level is still under 70 mg/dL (3.9 mmol/L), eat or drink another 15 grams of fast-acting carbohydrate. Recheck your blood sugar level again in 15 minutes. Repeat these steps until your blood sugar is at a safe level. It should be above at least 70 mg/dL (3.9 mmol/L) but usually above 90 mg/dL (5 mmol/L).
  • Have a snack or meal. Once your blood sugar is back in a safe range, eat a healthy snack or meal that includes protein and carbohydrates. This can help prevent another drop in blood sugar. It also replaces your body's stored glycogen.

How to treat severe hypoglycemia right away

Severe hypoglycemia is when you need help from someone to recover. For example, if you can't eat, you might need a glucagon injection or intravenous glucose.

In general, people with diabetes who are treated with insulin should have a glucagon kit for emergencies. Family and friends need to know where to find the kit and how to use it in an emergency.

If you're helping someone who has fainted or cannot safely swallow, don't try to give the person food or drink. If there's no glucagon kit available or if you don't know how to use one, call 911 or your local emergency services number for medical help.

Treatment of a condition causing hypoglycemia

If you have hypoglycemia that happens often, your healthcare professional looks for the condition causing hypoglycemia and treats it. Depending on the cause, treatment may include:

  • Nutrition counseling. A review of eating habits and food planning with a registered dietitian may help prevent hypoglycemia.
  • Medicines. If a medicine is the cause of your hypoglycemia, your healthcare professional may suggest adding, changing or stopping a medicine or changing the dose.
  • Tumor treatment. A tumor in your pancreas is typically treated with surgery to take it out. Another option is to destroy tumor tissue with heat or with a chemical placed in the tumor. Rarely, medicines are used to control hypoglycemia.

Preparing for an appointment

If you have diabetes and you're often having periods of hypoglycemia, or if your blood sugar levels often drop, talk with your healthcare professional to find out how you might need to change your diabetes treatment plan.

If you haven't been diagnosed with diabetes, make an appointment with your healthcare professional to find the cause of your symptoms of hypoglycemia and get treatment.

Here's some information to help you get ready for your appointment. Take a family member or friend along, if possible. Someone who goes with you can help you remember information you're given.

What you can do

Before your appointment:

  • Make a list of your hypoglycemia symptoms, including when they started and how often they happen. Also include when they happen, such as when fasting, after eating or both. Note what treatment helps your hypoglycemia symptoms and what you tried that didn't help.
  • List your key medical information, including other conditions for which you're being treated. Also list the names of all medicines, vitamins and other supplements you take, including doses.
  • Provide your diabetes treatment information if you have diabetes. Include the timing and results of recent blood sugar tests and when you take any medicines you use.
  • List your typical daily habits, including how often you drink alcohol and how much. Also include your usual meals and exercise routines. Note recent changes to these habits, such as a new exercise routine or a new job that's changed the times you eat.
  • Make a list of questions to ask your healthcare professional.

Questions to ask if you have diabetes include:

  • Are my symptoms due to hypoglycemia?
  • What do you think is causing my hypoglycemia?
  • What things can I do to alert me that I have hypoglycemia?
  • What things can I do to prevent hypoglycemia?
  • Do I need to adjust my diabetes treatment plan?
  • Do I need to change my eating or exercise routine?
  • I have other health conditions. How can I manage these conditions together?

Questions to ask if you have not been diagnosed with diabetes include:

  • Is hypoglycemia the most likely cause of my symptoms?
  • What else might be the cause?
  • What tests do I need?
  • What self-care steps, including lifestyle changes, can I take to help my symptoms get better?
  • Should I see a specialist?

What to expect from your doctor

Your healthcare professional might ask you questions, such as:

  • What symptoms have you been having?
  • When do your symptoms typically happen?
  • Does anything seem to make your symptoms worse? Does anything make them better?
  • Have you been diagnosed with other medical conditions?
  • What medicines are you currently taking?

Be ready to answer questions so that you have time to talk about what's most important to you.

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