Heat exhaustion is a condition whose symptoms may include heavy sweating and a rapid pulse, a result of your body overheating. It's one of three heat-related syndromes, with heat cramps being the mildest and heatstroke being the most severe.
Causes of heat exhaustion include exposure to high temperatures, particularly when combined with high humidity, and strenuous physical activity. Without prompt treatment, heat exhaustion can lead to heatstroke, a life-threatening condition. Fortunately, heat exhaustion is preventable.
Signs and symptoms of heat exhaustion may develop suddenly, or over time, especially with prolonged periods of exercise. Possible heat exhaustion symptoms include:
When to see a doctor
Contact your doctor if your signs or symptoms worsen or if they don't improve within one hour. Seek immediate medical attention if your body temperature reaches 104 F (40 C) or higher.
Your body's heat combined with environmental heat results in what's called your core temperature — your body's internal temperature. Your body needs to regulate the heat gain (and in cold weather, heat loss) from the environment to maintain a core temperature that's normal, approximately 98.6 F (37 C).
Your body's failure to cool itself
As a result, your body may develop heat cramps, the mildest form of heat-related illness. Signs and symptoms of heat cramps usually include heavy sweating, fatigue, thirst and muscle cramps. Prompt treatment usually prevents heat cramps from progressing to heat exhaustion.
You usually can treat heat cramps by drinking fluids containing electrolytes (such as Gatorade or other sports drinks), getting into cooler temperatures, such as an air-conditioned or shaded place, and resting.
Anyone can develop heat exhaustion, but certain factors increase your sensitivity to heat. They include:
Untreated, heat exhaustion can lead to heatstroke, a life-threatening condition that occurs when your body temperature reaches 104 F (40 C) or higher. Heatstroke requires immediate medical attention to prevent permanent damage to your brain and other vital organs that can result in death.
Tests and diagnosis
If you need medical attention due to heat exhaustion, it may be apparent to medical personnel that you have heat exhaustion, or they may take your temperature to confirm the diagnosis and rule out heatstroke. If your doctors suspect your heat exhaustion may have progressed to heatstroke, you may need additional tests, including:
Treatments and drugs
In most cases, you can treat heat exhaustion yourself by doing the following:
If you don't begin to feel better within one hour of using these treatment measures, seek prompt medical attention. You may be given intravenous (IV) fluids to help you rehydrate. Immersing you in cold water, misting your skin, placing you in front of fans, or using cold or ice packs and cooling blankets are some of the techniques that may be used to bring down your body temperature.
You can take a number of precautions to prevent heat exhaustion and other heat-related illnesses. When temperatures climb, remember to:
It's best not to exercise or do any strenuous activity in hot weather, but if you must, follow the same precautions and rest frequently in a cool spot. Taking breaks and replenishing your fluids during that time will help your body regulate your temperature.
Last Updated: 2011-11-18
© 1998-2015 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.com," "Mayo Clinic Health Information," "Reliable information for a healthier life" and the triple-shield Mayo logo are trademarks of Mayo Foundation for Medical Education and Research.
Terms and conditions of use