Symptoms and Signs of Heat Exhaustion vs. Heatstroke

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Medically Reviewed on 5/20/2022

Doctor's Notes on Heat Exhaustion vs. Heat Stroke: How to Tell the Difference

Heat exhaustion and heatstroke are related conditions that develop when a person's body becomes overheated because the body cannot cool itself rapidly enough to prevent an increased body core temperature. The signs and symptoms for heat exhaustion are usually the same for early heatstroke; however, heatstroke has additional life-threatening signs and symptoms. Heat exhaustion symptoms and signs are as follows:

  • pale, cool and clammy skin;
  • profuse sweating;
  • dizziness or lightheadedness; and
  • a core body temperature (best measured by a rectal thermometer) of more than 100 F (37.7 C) but not above 104 F (40 C).

These can be considered early warning signs of heatstroke if the patient tries to continue activity and is not treated. Heatstroke signs and symptoms are worsening of the above resulting in

The heatstroke patient can also develop blood pressure changes (high or low levels), hyperventilation, coma, and death.

The cause of both heat exhaustion and heatstroke is the body's inability to cool its core temperature to keep it in a normal range. Work or play in a humid and hot environment where sweating cannot cool the body leads to dehydration and potentially rapid onset of symptoms that need urgent and/or emergent care.

What Are the Treatments for Heat Exhaustion and Heatstroke?

The treatment for heat exhaustion begins when a person first suspects the problem. Immediate treatment steps include the following:

  • Get person out of heat into shade or air-conditioned area.
  • Lay person on back and elevate feet and legs slightly.
  • Remove tight or heavy clothing.
  • Person should drink cool water (no alcohol or caffeine).
  • Cool person by spraying, sponging, and fanning.
  • Monitor person for signs of heatstroke (see above).

The above steps may fail or not completed before heatstroke symptoms occur; the treatment of heatstroke includes the following:

  • Call 911 and at the same time accomplish the following.
  • Immerse person in cold water if available.
  • Cool person by spraying, sponging, and fanning.
  • Wrap person in cooling blanket.
  • Apply ice packs to groin, neck, back, and armpits.
  • If the person starts shivering, doctors may give a muscle relaxant to counteract the heat produced by muscle shivering.

Heatstroke is a medical emergency.

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Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.