Skip to Content

Hypoglycemia

Overview

Hypoglycemia is a condition caused by a very low level of blood sugar (glucose), your body's main energy source.

Hypoglycemia is often related to the treatment of diabetes. However, a variety of conditions — many rare — can cause low blood sugar in people without diabetes. Like fever, hypoglycemia isn't a disease itself — it's an indicator of a health problem.

Immediate treatment of hypoglycemia is necessary when blood sugar levels are at 70 milligrams per deciliter (mg/dL) or 3.9 millimoles per liter (mmol/L) or below. Treatment involves quick steps to get your blood sugar level back into a normal range either with high-sugar foods or drinks or with medications. Long-term treatment requires identifying and treating the underlying cause of hypoglycemia.

Symptoms

If blood sugar levels become too low, signs and symptoms may include:

  • An irregular heart rhythm
  • Fatigue
  • Pale skin
  • Shakiness
  • Anxiety
  • Sweating
  • Hunger
  • Irritability
  • Tingling sensation around the mouth
  • Crying out during sleep

As hypoglycemia worsens, signs and symptoms may include:

  • Confusion, abnormal behavior or both, such as the inability to complete routine tasks
  • Visual disturbances, such as blurred vision
  • Seizures
  • Loss of consciousness

People with severe hypoglycemia may appear as if they're intoxicated. They may slur their words and move clumsily.

When to see a doctor

Seek a doctor's help immediately if:

  • You have what may be symptoms of hypoglycemia and you don't have diabetes.
  • You have diabetes and hypoglycemia isn't responding to treatment. Initial treatment of hypoglycemia is drinking juice or regular soft drinks, eating candy or taking glucose tablets. If this treatment doesn't raise your blood sugar and improve your symptoms, contact your doctor right away.

Seek emergency help if:

  • Someone with diabetes or a history of recurring hypoglycemia has symptoms of severe hypoglycemia or loses consciousness

Causes

Hypoglycemia occurs when your blood sugar (glucose) level falls too low. There are several reasons why this may happen, the most common is a side effect of drugs used to treat diabetes.

Blood sugar regulation

But to understand how hypoglycemia happens, it helps to know how your body normally processes blood sugar. When you eat, your body breaks down carbohydrates from foods — such as bread, rice, pasta, vegetables, fruit and milk products — into various sugar molecules, including glucose.

Glucose is the main energy source for your body, but it can't enter the cells of most of your tissues without the help of insulin — a hormone secreted by your pancreas. When glucose levels rise, certain cells (beta cells) in your pancreas release insulin. This allows glucose to enter the cells and provide the fuel your cells need to function properly. Any extra glucose is stored in your liver and muscles in the form of glycogen.

If you haven't eaten for several hours and your blood sugar level drops, another hormone from your pancreas called glucagon signals your liver to break down the stored glycogen and release glucose back into your bloodstream. This keeps your blood sugar level within a normal range until you eat again.

Aside from your liver breaking down glycogen into glucose, your body also has the ability to manufacture glucose. This process occurs primarily in your liver, but also in your kidneys.

Possible causes, with diabetes

People with diabetes may not make enough insulin (type 1 diabetes) or may be less responsive to it (type 2 diabetes). As a result, glucose tends to build up in the bloodstream and may reach dangerously high levels. To correct this problem, someone with diabetes may take insulin or other drugs to lower blood sugar levels.

But too much insulin or other diabetes medications may cause your blood sugar level to drop too low, causing hypoglycemia. Hypoglycemia may also happen if you don't eat as much food as usual after taking diabetes medication, or if you exercise more than you normally would.

Possible causes, without diabetes

Hypoglycemia in people without diabetes is much less common. Causes may include the following:

  • Medications. Taking someone else's oral diabetes medication accidentally is a possible cause of hypoglycemia. Other medications may cause hypoglycemia, especially in children or in people with kidney failure. One example is quinine (Qualaquin), which is used to treat malaria.
  • Excessive alcohol consumption. Drinking heavily without eating can block your liver from releasing stored glucose into your bloodstream, causing hypoglycemia.
  • Some critical illnesses. Severe illnesses of the liver, such as severe hepatitis, can cause hypoglycemia. Disorders of the kidney, which can keep your body from properly excreting medications, can affect glucose levels due to a buildup of those medications. Long-term starvation, as may occur in the eating disorder anorexia nervosa, can result in the depletion of substances your body needs to generate glucose (gluconeogenesis), causing hypoglycemia.
  • Insulin overproduction. A rare tumor of the pancreas (insulinoma) may cause overproduction of insulin, resulting in hypoglycemia. Other tumors may result in excessive production of insulin-like substances. Enlargement of beta cells of the pancreas that produce insulin (nesidioblastosis) may result in excessive insulin release, causing hypoglycemia.
  • Hormone deficiencies. Certain disorders of the adrenal glands and the pituitary gland can result in a deficiency of key hormones that regulate glucose production. Children may experience hypoglycemia if they have a deficiency of growth hormone.

Hypoglycemia after meals

Hypoglycemia usually occurs when you haven't eaten (when you're in a fasting state), but that's not always the case. Sometimes hypoglycemia occurs after meals because the body produces more insulin than is needed.

This type of hypoglycemia, called reactive or postprandial hypoglycemia, may occur in people who have had stomach surgery. It may also occur in people who haven't had this surgery.

Complications

If you ignore the symptoms of hypoglycemia too long, you may lose consciousness. That's because your brain needs glucose to function properly.

Recognize the signs and symptoms of hypoglycemia early because untreated hypoglycemia can lead to:

  • Seizure
  • Loss of consciousness
  • Death

Hypoglcemia can also contribute to:

  • Falls
  • Injuries
  • Motor vehicle accidents

Hypoglycemia unawareness

Over time, repeated episodes of hypoglycemia can lead to hypoglycemia unawareness. The body and brain no longer produce signs and symptoms that warn of a low blood sugar, such as shakiness or irregular heartbeats. When this happens, the risk of severe, life-threatening hypoglycemia is increased.

Undertreated diabetes

If you have diabetes, episodes of low blood sugar are uncomfortable and can be frightening. Repeated episodes of hypoglycemia may cause you to take less insulin to ensure that your blood sugar level doesn't go too low. But long-term high blood sugar levels can be dangerous too, possibly causing damage to your nerves, blood vessels and various organs.

Prevention

  • If you have diabetes, carefully follow the diabetes management plan you and your doctor have developed. If you're taking new medications, changing your eating or medication schedules, or adding new exercise, talk to your doctor about how these changes might affect your diabetes management and your risk of low blood sugar.

    A continuous glucose monitor (CGM) is an option for some people, particularly those with hypoglycemia unawareness. These devices insert a tiny wire under the skin that can send blood glucose readings to a receiver.

    If blood sugar levels are dropping too low, some models of CGM will alert you with an alarm. Some insulin pumps are now integrated with CGMs and can shut off insulin delivery when blood sugar levels are dropping too quickly to help prevent hypoglycemia.

    Be sure to always have a fast-acting carbohydrate with you, such as juice or glucose tablets so that you can treat a falling blood sugar before it dips dangerously low.

  • If you don't have diabetes but have recurring episodes of hypoglycemia, eating frequent small meals throughout the day is a stopgap measure to help prevent your blood sugar levels from getting too low. However, this approach isn't an advisable long-term strategy. Work with your doctor to identity and treat the underlying cause of hypoglycemia.

Continuous glucose monitor

A continuous glucose monitor (CGM) is a device that measures your blood sugar every few minutes using a sensor inserted under the skin.

Diagnosis

If you use insulin or another diabetes medication known to lower blood sugar, and you have signs and symptoms of hypoglycemia, test your blood sugar levels with a blood glucose meter. If the result shows low blood sugar (under 70 mg/dL), treat accordingly.

If you don't use medications known to cause hypoglycemia, your doctor will want to know:

  • What were your signs and symptoms? You may not exhibit signs and symptoms of hypoglycemia during your initial visit with your doctor. In this case, your doctor may have you fast overnight (or for a longer period). This will allow low blood sugar symptoms to occur so that he or she can make a diagnosis.

    It's also possible that you'll need to undergo an extended fast in a hospital setting. Or if your symptoms occur after a meal, your doctor will want to test your glucose levels after a meal.

  • What is your blood sugar level when you're having symptoms? Your doctor will draw a sample of your blood to be analyzed in the laboratory.
  • Do your symptoms disappear when blood sugar levels increase?

In addition, your doctor will likely conduct a physical examination and review your medical history.

Treatment

Treatment of hypoglycemia involves:

  • Immediate initial treatment to raise your blood sugar level
  • Treatment of the underlying condition that's causing your hypoglycemia to prevent it from recurring

Immediate initial treatment

The initial treatment depends on your symptoms. Early symptoms can usually be treated by consuming 15 to 20 grams of a fast-acting carbohydrate.

Fast-acting carbohydrates are foods that are easily converted to sugar in the body, such as glucose tablets or gel, fruit juice, regular — not diet — soft drinks, and sugary candy such as licorice. Foods containing fat or protein aren't good treatments for hypoglycemia, because they affect the body's absorption of sugar.

Recheck blood sugar levels 15 minutes after treatment. If blood sugar levels are still under 70 mg/dL (3.9 mmol/L), treat with another 15 to 20 grams of fast-acting carbohydrate, and recheck the blood sugar level again in 15 minutes. Repeat these steps until the blood sugar is above 70 mg/dL (3.9 mmol/L).

Once the blood sugar levels are back to normal, it's important to have a snack or meal to help stabilize your blood sugar. This also helps the body replenish glycogen stores that may have been depleted during hypoglycemia.

If your symptoms are more severe, impairing your ability to take sugar by mouth, you may need an injection of glucagon or intravenous glucose. Do not give food or drink to someone who is unconscious, as he or she may aspirate these substances into the lungs.

If you're prone to severe episodes of hypoglycemia, ask your doctor if a home glucagon kit might be appropriate for you. In general, people with diabetes who are treated with insulin should have a glucagon kit for low blood sugar emergencies. Family and friends need to know where to find the kit, and need to be taught how to use it before an emergency occurs.

Treatment of the underlying condition

Preventing recurrent hypoglycemia requires your doctor to identify the underlying condition and treat it. Depending on the underlying cause, treatment may involve:

  • Medications. If a medication is the cause of your hypoglycemia, your doctor will likely suggest changing the medication or adjusting the dosage.
  • Tumor treatment. A tumor in your pancreas is treated by surgical removal of the tumor. In some cases, partial removal of the pancreas is necessary.

Preparing for an appointment

Hypoglycemia is common in type 1 diabetes, with symptomatic hypoglycemia occurring an average of twice a week. But if you notice that you're having more hypoglycemia, or if your blood sugar levels are dropping significantly lower, talk with your doctor to find out how you might need to change your diabetes management.

If you haven't been diagnosed with diabetes, make an appointment with your primary care doctor.

The following information will help you prepare for your appointment, and understand what to expect from your doctor.

What you can do

  • Write down your symptoms, including when they started and how often they occur.
  • List your key medical information, including any other conditions for which you're being treated and the names of any medications, vitamins or supplements you're taking.
  • Log details about your recent diabetes management if you have diabetes. Include the timing and results of recent blood sugar tests, as well as the schedule on which you've been taking your medications, if any.
  • List your typical daily habits, including alcohol intake, meals and exercise routines. Also, note any recent changes to these habits, such as a new exercise routine, or a new job that's changed the times you eat.
  • Take a family member or friend along, if possible. Someone who accompanies you may remember something that you missed or forgot.
  • Write down questions to ask your doctor. Creating your list of questions in advance can help you make the most of your time with your doctor.

Questions to ask your doctor if you have diabetes include:

  • Are my signs and symptoms due to hypoglycemia?
  • What do you think is triggering my hypoglycemia?
  • Do I need to adjust my treatment plan?
  • Do I need to make any changes to my diet?
  • Do I need to make any changes to my exercise routine?
  • I have other health conditions. How can I best manage these conditions together?
  • What else do you recommend to help me better manage my condition?

Questions to ask if you haven't been diagnosed with diabetes include:

  • Is hypoglycemia the most likely cause of my signs and symptoms?
  • What else might be causing these signs and symptoms?
  • What tests do I need?
  • What are the possible complications of this condition?
  • How is this condition treated?
  • What self-care steps, including lifestyle changes, can I take to help improve my signs and symptoms?
  • Should I see a specialist?

What to expect from your doctor

A doctor who sees you for signs and symptoms of hypoglycemia is likely to ask you a number of questions. The doctor may ask:

  • What are your signs and symptoms, and when did you first notice them?
  • When do your signs and symptoms typically occur?
  • Does anything seem to provoke your signs and symptoms?
  • Have you been diagnosed with any other medical conditions?
  • What medications are you currently taking, including prescription and over-the-counter drugs, vitamins and supplements?
  • What is your typical daily diet?
  • Do you drink alcohol? If yes, how much?
  • What is your typical exercise routine?

Last updated: February 16th, 2018

© 1998-2018 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. Terms of use

Learn more about Hypoglycemia

Associated drugs

Symptoms and treatments

Hide