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When should you call 911 for heat illness?

Dr. Colin Little

Dr. Colin Little

MD, FAWM, Chief Medical Officer, GOES Health

The short answer

Call 911 right away for heat stroke: anyone who is overheated and confused, slurring their speech, or not fully conscious. Heat stroke is a medical emergency, so make the call and start cooling them while you wait. For heat exhaustion, start cooling them and get medical help if symptoms are severe or don't improve, since heat exhaustion can lead quickly to heat stroke in the wrong environment.

Heat stroke is a medical emergency, so call 911 for emergency medical care immediately.1

What tips you off is how the person is acting, not just how hot they are. Call 911 for anyone who is overheated and confused, slurring their words, or not fully conscious, since those point to heat stroke.1 While you wait for help, move them to a cool area and start cooling them right away. Getting into the shade, wetting their skin and fanning helps, but they need medical attention as soon as possible. 12

Heat exhaustion is usually a step below that. The person may be tired, lightheaded, or dizzy, but they can interact with you and aren't confused.12 Start cooling them and keep a close eye on their condition. Get them medical help if the symptoms are severe or don't improve, since heat exhaustion can move to heat stroke quickly. 12

When you are unsure which one you are looking at, let the person's head decide. Clear-headed points to heat exhaustion; confused or fading points to heat stroke, and that's a 911 call every time.

Sources

  1. [1] US Centers for Disease Control and Prevention / NIOSH. Heat-related Illnesses (NIOSH Heat Stress). Accessed August 6, 2026. https://www.cdc.gov/niosh/heat-stress/about/illnesses.html
  2. [2] US National Park Service. Hike Smart — Grand Canyon National Park. Accessed August 5, 2026. https://home.nps.gov/grca/planyourvisit/hike-smart.htm

About the author

Dr. Colin Little

Dr. Colin Little

MD, FAWM, Chief Medical Officer, GOES Health

  • Board Certified Emergency Physician
  • Fellow of the Academy of Wilderness Medicine (FAWM)
  • Wilderness Medicine Fellowship, University of Utah
  • Emergency Medicine Residency and Chief Resident, Stanford / Kaiser
  • Doctor of Medicine, University of Arizona College of Medicine – Phoenix
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What are the warning signs of heat stroke?

The clearest warning sign of heat stroke is a change in mental state (confusion, slurred speech, or passing out) in someone who is overheated. Other signs are a very high body temperature, hot skin (dry or sweaty), a rapid strong pulse, and sometimes seizures. Heat stroke is a medical emergency: call 911 and start cooling the person right away.

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What separates heat stroke from heat exhaustion is altered mental status, a change in how clearly the person thinks . Heat exhaustion leaves the nervous system uninjured, so the person still makes sense and can answer you . Heat stroke adds confusion, slurred speech, seizures or loss of consciousness . Treat that change as an emergency. Cool the person immediately and call for help .

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