By Mayo Clinic Staff
Hypoglycemia is a condition characterized by an abnormally low level of blood sugar (glucose), your body's main energy source.
Hypoglycemia is commonly associated with the treatment of diabetes. However, a variety of conditions, many of them 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 involves quick steps to get your blood sugar level back into a normal range — about 70 to 110 milligrams per deciliter, or mg/dL (3.9 to 6.1 millimoles per liter, or mmol/L) — either with high-sugar foods or medications. Long-term treatment requires identifying and treating the underlying cause of hypoglycemia.
Similar to the way a car needs gas to run, your body and brain need a constant supply of sugar (glucose) to function properly. If glucose levels become too low, as occurs with hypoglycemia, it can cause these signs and symptoms:
- Heart palpitations
- Pale skin
- 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
- Loss of consciousness
People with severe hypoglycemia may appear as if they're intoxicated. They may slur their words and move clumsily.
Many conditions other than hypoglycemia may cause these signs and symptoms. A blood sample to test your blood sugar level at the time of these signs and symptoms is how to know for sure that hypoglycemia is the cause.
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:
- If someone with diabetes or a history of recurring hypoglycemia has symptoms of severe hypoglycemia or loses consciousness
Hypoglycemia occurs when your blood sugar (glucose) level falls too low. There are several reasons why this may happen, the most common being a side effect of drugs used for the treatment of diabetes. But to understand how hypoglycemia happens, it helps to know how your body normally regulates blood sugar production, absorption and storage.
Blood sugar regulation
During digestion, your body breaks down carbohydrates from foods — such as bread, rice, pasta, vegetables, fruit and milk products — into various sugar molecules. One of these sugar molecules is glucose, the main energy source for your body. Glucose is absorbed into your bloodstream after you eat, but it can't enter the cells of most of your tissues without the help of insulin — a hormone secreted by your pancreas.
When the level of glucose in your blood rises, it signals certain cells (beta cells) in your pancreas, located behind your stomach, to release insulin. The insulin, in turn, unlocks your cells so that glucose can enter 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.
This process lowers the level of glucose in your bloodstream and prevents it from reaching dangerously high levels. As your blood sugar level returns to normal, so does the secretion of insulin from your pancreas.
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 in a process called gluconeogenesis. This process occurs primarily in your liver, but also in your kidneys, and makes use of various substances that are precursors to glucose.
Possible causes, with diabetes
If you have diabetes, the effects of insulin on your body are drastically diminished, either because your pancreas doesn't produce enough of it (type 1 diabetes) or because your cells are less responsive to it (type 2 diabetes). As a result, glucose tends to build up in your bloodstream and may reach dangerously high levels. To correct this problem, you likely take insulin or other drugs designed to lower blood sugar levels.
If you take too much insulin relative to the amount of glucose in your bloodstream, it can cause your blood sugar level to drop too low, resulting in hypoglycemia. Hypoglycemia may also result if, after taking your diabetes medication, you don't eat as much as usual (ingesting less glucose) or you exercise more (using up more glucose) than you normally would. To prevent this from happening, it's likely that your doctor will work with you to find the optimum dosage that fits your regular eating and activity habits.
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 in 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 with these disorders are more prone to hypoglycemia than are adults.
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.
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:
- Loss of consciousness
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.
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.
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 provider.
Here's some information to help you get ready for your appointment and know 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 both conditions?
- 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?
Your doctor will use three criteria — often referred to as Whipple's triad — to diagnose hypoglycemia. Whipple's triad includes the following factors:
Signs and symptoms of hypoglycemia. 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 hypoglycemic 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.
- Documentation of low blood glucose when the signs and symptoms occur. Your doctor will draw a sample of your blood to be analyzed in the laboratory.
- Disappearance of the signs and symptoms. The third part of the diagnostic triad involves whether your signs and symptoms go away when blood glucose levels are raised.
In addition, your doctor will likely conduct a physical examination and review your medical history.
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 candy, fruit juice, regular — not diet — soft drinks, or glucose tablets or gel. Foods containing fat or protein aren't good treatments for hypoglycemia, because protein and fat can slow 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 the 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.
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 sends blood glucose readings to a receiver every five minutes or so. If blood sugar levels are dropping too low, the CGM alerts you with an alarm.
Be sure to always have a fast-acting carbohydrate with you, such as juice or glucose tablets, so 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.
Jan. 20, 2015
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