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.