What’s the Difference between Heat Stroke & Heat Exhaustion?

By Christoffer K. Birn, MD March 29, 2017

Even though many of us welcome warm temperatures and the chance to be outside in the sun, summer heat isn’t all fun and games.

If you plan on being outdoors, and especially if you’re planning on being active, it’s important to know the signs of heat-related illnesses like heat stroke and heat exhaustion. Both conditions occur when the body becomes dehydrated in hot or humid environments, but the combinations of symptoms differ between the two.

Symptoms of Heat Exhaustion

Heat exhaustion happens when the body is overheated, usually with a fever of up to 104 degrees Fahrenheit. One of the differences in symptoms between heat exhaustion and heat stroke is sweat; heat exhaustion is characterized by heavy sweating, while those suffering from heatstroke experience decreased sweating. Other symptoms of heat exhaustion are:

  • Agitation
  • Cool and clammy skin
  • Confusion or anxiety
  • Dizziness
  • Excessive thirst
  • Fainting
  • Headache
  • Muscle aches and cramps
  • Nausea
  • Slow heartbeat
  • Weakness and fatigue

Symptoms of Heat Stroke

Heat stroke occurs when the body’s temperature rises so much that the cooling system stops working altogether. This typically happens at body temperatures of 104-106 degrees Fahrenheit, but keep in mind that it can occur suddenly. It is possible for your body to overheat so quickly that it skips past the symptoms of heat exhaustion and goes straight to heatstroke.

As mentioned above, heatstroke is characterized by decreased sweating, as well as hot, flushed skin. Other symptoms include:

  • Confusion, delirium or loss of consciousness
  • Convulsions
  • Decreased urination and/or blood in urine or stool
  • Dizziness or vertigo
  • Fatigue
  • Headache
  • Nausea and vomiting
  • Rapid heart rate
  • Shortness of breathe

As you can see, there are common symptoms for both of these conditions, but the main differences in symptoms can be compared by heart rate and sweat. Heat exhaustion includes slow heartbeat, clamminess, heavy sweating and a desire for water. Heat stroke, on the other hand, includes fast heartbeat, decreased urination and decreased sweating.

  • Slow and sweaty = heat exhaustion
  • Fast and dry = heatstroke

Remember that heat exhaustion and heat stroke are potentially life threatening. If you or someone near you shows any symptoms, get them out of the heat and seek medical attention immediately.