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Harvard Commentaries
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Reviewed by the Faculty of Harvard Medical School

Food for Thought Food for Thought


January 16, 2013

By Laura J. Hodgdon, Dietetic Intern
Brigham and Women's Hospital

Have you ever skipped a meal and felt shaky, dizzy, confused and, more importantly, hungry? If you have, you are not alone. These are symptoms of hypoglycemia, also called low blood sugar. It is usually a result of skipping meals.

Hypoglycemia is uncommon in adults and children older than 10 years, except as a side effect of diabetes treatment. But it can also result from increased exercise or other physical activity, or drinking alcohol on an empty stomach. Other more rare conditions that may lead to hypoglycemia include insulin-secreting tumors of the pancreas and diseases like cirrhosis and hepatitis.

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What Is Hypoglycemia?

Normally, the body converts carbohydrates in food into a sugar called glucose. Glucose is the main sugar found in blood and is a source of energy for the body and brain.

Foods that are rich in carbohydrates include, but are not limited to:

  • Rice, potatoes and pasta
  • Corn, peas and beans
  • Bread, rolls and tortillas
  • Cereal and cereal bars
  • Milk, fruit and fruit juice
  • Cookies, candies and sweets

Hypoglycemia occurs when blood glucose levels drop below 70 mg/dL.

There are two types of hypoglycemia.

1. Fasting hypoglycemia

When the body goes without food — usually for more than six hours — levels of sugar in the blood drop. This type of hypoglycemia is often seen in heavy drinkers who do not eat; in people with viral hepatitis, cirrhosis, or liver cancer; and in children with carbohydrate metabolic disorders.

Generally, when blood glucose begins to fall, a hormone called glucagon is secreted from the pancreas. Glucagon's job is to signal the liver to break down glycogen — the form glucose takes when it is stored in the body — and release glucose into the bloodstream. This keeps your blood sugar level within a normal range until you eat again.

2. Postprandial hypoglycemia

This type of hypoglycemia is often caused by the body releasing too much insulin into the blood after eating a carbohydrate-rich meal or food.

Insulin carries glucose into the cells. When there is excessive insulin, too much glucose can move into the cells. This leaves too little glucose in the blood, so glucose levels drop significantly. People who are very thin, who have lost a lot of weight, and women who have most of their excess weight below their waists may have this type of hypoglycemia. A high-carbohydrate/low-fat diet or drinking too much alcohol, for example, may also cause postprandial hypoglycemia.

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Symptoms of Hypoglycemia

Hypoglycemia can cause one or more of the following symptoms:

  • Shakiness
  • Sense of weakness
  • Altered or depressed mood
  • Confusion
  • Fatigue
  • Anxiety
  • Paleness
  • Perspiration
  • Increased pulse or respiratory rate
  • Hunger
  • Blurred vision

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Treating Hypoglycemia

Hypoglycemia can happen suddenly. It is usually mild and can be treated quickly and easily.

The primary goal is to bring glucose levels up first. This can be done by eating or drinking a small amount (15 grams) of a glucose-rich food such as:

  • ½ cup orange juice or regular soda, such as cola
  • 6 to 8 jelly beans or lifesavers
  • 1 tablespoon of sugar, honey or syrup

For people with diabetes, a simple way to get blood glucose levels up is to follow the "15-15-15" rule. When blood glucose level is less than 70 mg/dL, eat or drink 15 grams of a glucose-rich food, wait 15 minutes and retest blood sugar, then take another 15 grams of carbohydrates if blood glucose level is still less than 70 mg/dL.

Whether you have diabetes or not, it's also important to include a protein with a carbohydrate/starch. This will slow the release of glucose into the bloodstream, so blood sugar levels stay level.

Here are some ways to do this:

Choose 1 protein

Choose 1 carbohydrate/starch

1-2 tablespoons of peanut butter or almond butter
1 slice whole-grain bread
¼ cup raw, unsalted nuts (almonds, walnuts, cashews, etc.)
1 fruit (apple, banana, orange, etc.)
1 ounce of low-fat cheese
5-7 whole-grain crackers

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Preventing Hypoglycemia

If you have diabetes, it's important to talk to your doctor about your diet, medications and exercise because they can all make your blood sugar rise or fall.

Too little food may result in hypoglycemia. Too much food may cause your blood sugar level to climb too high (hyperglycemia). Your doctor or registered dietitian can help you find just the right balance.

It's important to ask your doctor or pharmacist if any medications you are taking may affect your blood sugar level. Sometimes another medication may be recommended.

When you exercise, your muscles use sugar (glucose) for energy, which may lower your blood sugar level. It's important to check with your doctor about exercise, especially if you've been inactive and plan to start exercising regularly.

Planning ahead is the key to preventing hypoglycemia. Here are a few simple steps you can take everyday to help manage your blood sugar level.

  • Eat small, frequent, balanced meals. Aim to eat every three to four hours to keep blood sugar stable.
  • Pair a protein (meat, fish, chicken, cheese, nuts, peanut butter etc.) with a carbohydrate/whole grain at every meal and snack.
  • Limit alcoholic drinks to one per day if you are a woman and two drinks per day if you are a man. Alcohol tends to lower blood sugar and can cause hypoglycemia. Therefore, it is important to always have your drink with a meal or snack to avoid low blood sugar.
  • One drink means 5 ounces of wine, 12 ounces of beer or 1.5 ounces of hard liquor.
  • Discuss medication interactions with your doctor and/or pharmacist. Some medications may actually interact with food and/or alcohol. It's important for you to know if you need to avoid or limit certain foods to insure the medication is working properly.

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For More Information

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By Laura J. Hodgdon is a dietetic intern at Brigham and Women's Hospital

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