Heatstroke is a life-threatening condition that happens when your body temperature rises above 104 degrees Fahrenheit (40 degrees Celsius). It’s usually the result of overexertion in hot, humid conditions. Symptoms can include confusion, seizures or loss of consciousness. Untreated, heatstroke can lead to organ failure, a coma or death.
Heatstroke is a life-threatening condition that causes your body to overheat. It’s defined as a body temperature above 104 degrees Fahrenheit (40 degrees Celsius). Heatstroke, also called sunstroke, is the most severe form of hyperthermia, or heat-related illness. Heatstroke can lead to brain damage, organ failure or death.
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There are two types of heatstroke:
Heat exhaustion and heatstroke are both types of hyperthermia. Heat exhaustion can develop into heatstroke if left untreated. But heat exhaustion isn’t as severe as heatstroke, doesn’t cause neurological problems and usually isn’t life-threatening.
Anyone can get heatstroke. But infants and the elderly are at especially high risk because their bodies may not be able to regulate temperature effectively. Athletes, soldiers and people with occupations that require physical labor in hot environments are also susceptible to heatstroke.
Other factors that increase your risk of heatstroke include:
Studies suggest that heatstroke occurs in about 20 out of 100,000 people each year in the U.S. It’s most common in urban areas during periods of very hot weather. Heatstroke causes between 240 and 833 deaths in the U.S. annually.
Heatstroke occurs when your body can’t cool itself down. Your hypothalamus (a part of your brain that controls many bodily functions) sets your core body temperature. It typically sets your temperature at about 98.6 degrees Fahrenheit (37 degrees Celsius). But if your body takes in more heat than it releases, your internal temperature rises above this set-point.
Heatstroke is a medical emergency. If you or someone you know exhibits any of the following signs or symptoms, call 911 immediately:
People with heatstroke can develop shock or slip into a coma. High body temperature can lead to:
Healthcare providers typically diagnose heatstroke in the emergency department. They review your symptoms, perform a physical exam and take your temperature. They may also order blood tests or urinalysis. Additional tests might include a chest X-ray or electrocardiogram (EKG) to monitor the electrical activity in your heart.
Heatstroke requires immediate medical treatment. If you’re waiting for an ambulance to arrive, try to cool the person as much as possible by:
At the hospital, the person with heatstroke may receive:
Sometimes cold-water lavage is necessary. This treatment uses catheters (thin, flexible tubes) to fill body cavities with cold water. This helps lower the body temperature overall. The catheter may go into the rectum or down the throat.
Healthcare providers stop cooling treatments once the body reaches about 102 degrees Fahrenheit (38.9 degrees Celsius). The length of time you stay in the hospital depends on the severity of your heatstroke and how well your organs are functioning.
In most cases, it’s possible to prevent heatstroke by:
Your outlook after heatstroke depends on a variety of factors, including:
Between 10 and 65% of people with non-exertional heatstroke die from the illness. The outlook is better for exertional heatstroke, which has a mortality rate of 3 to 5%. Some people experience permanent organ damage or neurological dysfunction.
During your recovery after heatstroke, you can expect changes in your body temperature for several weeks. You should avoid physical activity for at least a week. You will also need periodic tests to monitor your kidney and liver function. Even temporary complications of heatstroke can take several months to go away.
After you’ve had heatstroke once, you’re more likely to get this heat illness again. Take preventive measures any time you plan to be in hot conditions.
If you’ve had heatstroke and are recovering, contact your doctor right away if you experience anything abnormal such as:
A note from Cleveland Clinic
Heatstroke is a life-threatening condition that occurs when your body temperature gets too high. It’s usually the result of overexertion in hot, humid weather. Symptoms may include confusion, seizures or loss of consciousness, among others. If you or someone you know has heatstroke, seek immediate medical attention and try to lower the person’s body temperature as quickly as possible.
Last reviewed by a Cleveland Clinic medical professional on 09/13/2021.
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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy