Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link
What Is Heatstroke?
What Is Heatstroke?
What Is Heatstroke?

    Heatstroke is a medical emergency caused by your body temperature going too high.

    If you don't cool down quickly enough, heatstroke can damage your organs, such as your brain, heart, and lungs. It could also lead to death.

    Heatstroke can affect anyone. Those at increased risk include older people who are shut in a hot room without air conditioning even if the room doesn't seem very hot; someone locked in a hot car, particularly children who are too young to open the door (cars are known to heat up very quickly inside, especially in the sun); and athletes and people working in high heat.

    If you are getting sick from the heat, you may not realize that your body temperature is too high.

    You may have these warning signs of heatstroke:

    • Weakness, dizziness, or light-headedness

    • Headache

    • Feeling sick to your stomach

    • Throwing up

    If your skin is hot, flushed, or dry and you are showing signs of confusion, these are indicators of heat stroke. You may or may not be sweaty if you have heatstroke.

    Heatstroke is diagnosed based on what happened to you, your symptoms, and your body temperature. Your doctor will do blood and urine tests to see if your organs are working right.

    To prevent heatstroke when it's hot outside, it's important to wear lightweight clothes that aren't too tight, stay out of the sun as much as you can, drink plenty of fluids even if you don't feel thirsty, and avoid heavy exercise in the hottest part of the day.

    Ask your doctor if any of your health problems or medicines may raise your risk of heatstroke.

    Check on older people, especially those who don't have air conditioning, and never leave a young child in a parked car.

    If you know you're going to have to work or exercise in the heat, get your body used to the heat gradually. Being physically fit is different than being used to the heat.

Copyright © 2023 Merck & Co., Inc., Rahway, NJ, USA and its affiliates. All rights reserved.

In these topics
Quick Facts: Heatstroke