Overview

Hypoglycemia is a condition in which your blood sugar (glucose) level is lower than normal. Glucose is your body's main energy source.

Hypoglycemia is often related to diabetes treatment. But other drugs and a variety of conditions — many rare — can cause low blood sugar in people who don't have diabetes

Hypoglycemia needs immediate treatment when blood sugar levels are low. For many people, a fasting blood sugar of 70 milligrams per deciliter (mg/dL), or 3.9 millimoles per liter (mmol/L), or below should serve as an alert for hypoglycemia. But your numbers might be different. Ask your doctor.

Treatment involves quickly getting your blood sugar back to normal either with high-sugar foods or drinks or with medications. Long-term treatment requires identifying and treating the cause of hypoglycemia.

Symptoms

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

  • An irregular or fast heartbeat
  • Fatigue
  • Pale skin
  • Shakiness
  • Anxiety
  • Sweating
  • Hunger
  • Irritability
  • Tingling or numbness of the lips, tongue or cheek

As hypoglycemia worsens, signs and symptoms can include:

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

When to see a doctor

Seek a doctor's help immediately if:

  • You have what might be hypoglycemia symptoms and you don't have diabetes
  • You have diabetes and hypoglycemia isn't responding to treatment, such as drinking juice or regular soft drinks, eating candy, or taking glucose tablets

Seek emergency help for someone with diabetes or a history of hypoglycemia who 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 can happen; the most common is a side effect of drugs used to treat diabetes.

Blood sugar regulation

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, the main energy source for your body, enters the cells of most of your tissues with the help of insulin — a hormone secreted by your pancreas. Insulin enables the glucose to enter the cells and provide the fuel your cells need. 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 signals your liver to break down the stored glycogen and release glucose into your bloodstream. This keeps your blood sugar within a normal range until you eat again.

Your body also has the ability to make glucose. This process occurs mainly in your liver, but also in your kidneys.

Possible causes, with diabetes

If you have diabetes, you might not make enough insulin (type 1 diabetes) or you might be less responsive to it (type 2 diabetes). As a result, glucose tends to build up in the bloodstream and can reach dangerously high levels. To correct this problem, you might 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 can also occur if you eat less than usual after taking diabetes medication, or if you exercise more than you normally do.

Possible causes, without diabetes

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

  • Medications. Taking someone else's oral diabetes medication accidentally is a possible cause of hypoglycemia. Other medications can cause hypoglycemia, especially in children or in people with kidney failure. One example is quinine (Qualaquin), used to treat malaria.
  • Excessive alcohol drinking. Drinking heavily without eating can block your liver from releasing stored glucose into your bloodstream, causing hypoglycemia.
  • Some critical illnesses. Severe liver illnesses such as severe hepatitis or cirrhosis can cause hypoglycemia. Kidney disorders, which can keep your body from properly excreting medications, can affect glucose levels due to a buildup of those medications.

    Long-term starvation, as can occur in the eating disorder anorexia nervosa, can result in too little of substances your body needs to create glucose.

  • Insulin overproduction. A rare tumor of the pancreas (insulinoma) can cause you to produce too much insulin, resulting in hypoglycemia. Other tumors also can result in too much production of insulin-like substances. Enlargement of cells of the pancreas that produce insulin can result in excessive insulin release, causing hypoglycemia.
  • Hormone deficiencies. Certain adrenal gland and pituitary tumor disorders can result in a deficiency of key hormones that regulate glucose production. Children can have hypoglycemia if they have too little growth hormone.

Hypoglycemia after meals

Hypoglycemia usually occurs when you haven't eaten, but not always. Sometimes hypoglycemia symptoms occur after certain meals high in sugar because your body produces more insulin than you need.

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

Complications

Untreated hypoglycemia can lead to:

  • Seizure
  • Loss of consciousness
  • Death

Hypoglycemia can also contribute to the following:

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

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 increases.

If you have diabetes, recurring episodes of hypoglycemia and hypoglycemia unawareness, your doctor might modify your treatment, raise your blood sugar level goals and recommend blood glucose awareness training.

Undertreated diabetes

If you have diabetes, episodes of low blood sugar are uncomfortable and can be frightening. Fear of hypoglycemia can cause you to take less insulin to ensure that your blood sugar level doesn't go too low. This can lead to uncontrolled diabetes. Talk to your doctor about your fear, and don't change your diabetes medication dose without your doctor's okay.

Prevention

If you have diabetes

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. A CGM has a tiny wire that's inserted 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 level before it dips dangerously low.

If you don't have diabetes

For 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 advised as a long-term strategy. Work with your doctor to identify and treat the cause of hypoglycemia.

March 13, 2020
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