Heat Exhaustion

Heat exhaustion is the most common type of heat-related illness. It can occur when you exercise or do manual labor in a hot environment, and your body struggles to cool itself down. When you have heat exhaustion, your internal (core) body temperature may be abnormally high, but it’s typically below 104 degrees Fahrenheit (40 degrees Celsius). You’ll likely sweat a lot and have other symptoms like dizziness, nausea and a headache.

Without treatment, heat exhaustion can turn into the most severe form of heat-related illness: heat stroke. A key difference between heat exhaustion and heat stroke is that with heat stroke, you have signs of brain dysfunction (encephalopathy). These include persistent confusion, changes in behavior (like aggression or agitation) and slurred speech. You’ll also have a dangerously high body temperature, typically above 104 degrees F.

If you or someone you’re with has signs of heat exhaustion or heat stroke, call 911 or your local emergency services number. Treating heat exhaustion is essential for preventing its progression to life-threatening heat stroke.