Please note: This information was current at the time of publication but now may be out of date. This handout provides a general overview and may not apply to everyone. 

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Am Fam Physician. 2002;65(11):2319-2320

What are heat-related illnesses?

There are three kinds of heat illnesses. They are heat cramps, heat exhaustion, and heatstroke. You might get one if your body gets too hot and you can't get cool. These illnesses can be severe or mild. Heat cramps are a mild form of heat-related illness. Heat exhaustion is a little worse. Heatstroke is the most dangerous form. If heat cramps are not treated, they can turn into heat exhaustion or heatstroke.

1. Heat Cramps

If you sweat too much and drink either too much or too little fluid, you can get painful muscle spasms (cramps). The cramps are often in the calf and abdominal (tummy) muscles. You can help prevent these cramps if you stretch your muscles before you exercise and drink enough fluids. An electrolyte solution such as a sports drink will replace lost salt.

2. Heat Exhaustion

If you do not drink enough fluids and you stay in the heat, you can get heat exhaustion. You will be dehydrated. You may feel lightheaded, nauseated, tired, anxious, and confused. You should move to a cool, shady place (or an air-conditioned room), put cold water or cold wet towels on your body, and drink cool liquids. If you are confused, lethargic, or have a fever, someone should take you to the hospital.

3. Heatstroke

It might be hard to tell you have heatstroke. You can have heatstroke even if you are not sweating. If you have heatstroke, your temperature will be very high. You will be confused. Heatstroke is a life-threatening emergency. You (or someone else) should call 911 right away. While you are waiting for the ambulance, try to go to a cool place, take off some clothing, and treat as you would for heat exhaustion (see number 2, above). If you can't do this by yourself, try to get someone to help you do it.

What can I do to prevent heat-related illnesses?

Drink 1 1/2 to 2 cups of fluids before working out. Drink two to four cups of fluids during each hour of physical activity. Try to exercise in the early morning or evening. Wear light clothes when it is hot. Before you run a long race in a warm climate, give yourself two weeks of practicing in the heat to get used to it. To see if it is safe for vigorous outdoor exercise, check a Heat Index Chart. You can find one at this Web address:

What makes me more likely to get a heat-related illness?

The following conditions make you more likely to get a heat-related illness:

  • Alcoholism

  • Heart problems

  • Cystic fibrosis

  • Dehydration

  • Eating disorders

  • Being very old or very young

  • Fever

  • Gastroenteritis

  • Low levels of potassium

  • Obesity

  • Sunburn

  • Not getting enough sleep

  • Uncontrolled diabetes

  • Uncontrolled high blood pressure

  • Uncontrolled thyroid disorder

  • Upper respiratory tract infection

If you have a health problem, you can lower your chances of getting a heat-related illness by getting treatment for your problem before you exercise.

Do any medicines make me more likely to get a heat-related illness?

Some medicines for allergies, heart conditions, and seizures may make you more likely to get a heat-related illness. Diuretics, sedatives, caffeine, and alcohol may also increase your risk. Ask your doctor or pharmacist if your medicines put you at risk for heat-related illness.

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Copyright © 2002 by the American Academy of Family Physicians.

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