By August Ryan; Medically reviewed by Nathalie May, MD
Heatstroke and heat exhaustion are both heat-related illnesses. But these are different conditions with different symptoms.
Heat exhaustion is a less serious illness. It can happen when you are dehydrated on a very hot or humid day. Heat exhaustion can cause:
- Heavy sweating
- Feeling weak
- Dizziness
- Headache
- Nausea or vomiting
- Muscle cramps
Heatstroke is very serious and can be fatal. It can happen when your body temperature rises to a dangerously high level. Heatstroke symptoms include:
- Body temperature above 104°F
- Heartbeat that is faster than normal
- Breathing that is faster than normal
- Headache
- Dizziness
- Nausea or vomiting
- Confusion
- Seizures
- Loss of consciousness (“blacking out/passing out”)
Heatstroke is an emergency. If you or someone you know has heatstroke symptoms, call 9-1-1- or go to the nearest emergency room right away.
While they wait for medical care, a person with heatstroke symptoms should sit in a cool and shaded area. They should take off any clothing they don’t need. They should drink cool water or use a fan to cool off.
Babies, young children, elderly people and people with chronic medical conditions are most likely to get heatstroke.
How to Avoid Heatstroke
Heatstroke is scary, but it is easy to protect yourself and others during hot weather.
Drink lots of water and fluids, especially if you are outside or exercising. Drink less alcohol and caffeine, and remember that tea and coffee both have caffeine. All caffeinated beverages can dehydrate you and raise your risk of heatstroke.
Spend the hottest parts of the day in shaded areas or indoors. It is usually hottest from 10 a.m. to 4 p.m. Minimize outdoor exercise when the temperature is above 90 degrees.
Wear lightweight, loose-fitting clothes. This allows your skin to breathe.
Take lots of breaks in cool and shaded areas. This is especially important if you are exercising or working outside.
Use fans or air conditioning to keep your environment cool.