Heat-Related Illness (when the body overheats) - Adults
Heat exhaustion or Heat stroke
What it is
During extreme heat or intense physical activity in a hot environment, the body may have difficulty cooling itself. When the body becomes too hot, symptoms may include headache, nausea, diarrhea (loose, watery stools), or cramps in the legs, arms, or abdomen. Heat stroke is the most severe form of heat-related illness. It can develop quickly and become life-threatening if left untreated. Body temperature rises to a dangerously high level, and the person may become confused, disoriented, unconscious, or experience seizures (uncontrolled shaking of the body). It is important to go to the hospital immediately if you notice any of these symptoms.
What you can do at home
What to do
- Move to a cool place as soon as possible, lie down, and rest (in an air-conditioned, well-ventilated area, or in the shade).
- Apply cool, non-icy water to the entire body.
- Apply ice packs to the neck, armpits, and groin.
- If cramps occur, loosen clothing and gently massage the affected muscle.
Staying hydrated
- Drink cool water frequently in small amounts, unless advised otherwise by a healthcare professional.
- Use an electrolyte replacement drink from the pharmacy (such as Pedialyte or Gastrolyte), or make your own:
- 360 mL unsweetened orange juice
- 600 mL cooled boiled water
- 2.5 mL (½ tsp) salt
- Drink lightly salted beverages, such as sports drinks (Gatorade, Powerade).
What to avoid
- Avoid intense physical activity for at least 12 hours.
- Do not take medication to reduce a fever.
- Do not apply alcohol to the skin.
When to go to the hospital right away
Fever
Rectal temperature is:
- 38°C (100.4°F) or higher in babies younger than 3 months
- 40°C (104°F) or higher in babies 3 months of age and older, children, and adults
Unconsciousness (unresponsive
Seizures (uncontrolled shaking of the body)
Sudden change in overall condition, including:
- unusual fatigue (drowsiness) or difficulty staying awake
- limited responsiveness to surroundings
- confusion, agitation, or unusual behavior
- reduced appetite and decreased thirst
- difficulty carrying out usual daily activities
Rapid breathing
Excessive thirst and no urination for more than 12 hours
Symptoms that do not improve or that worsen despite following these recommendations
Need help?
Call Info-Santé at 811, Option 1, to speak with a nurse at any time.
Go to the pharmacy for advice on medications or treatment.
Make an appointment at your medical clinic or CLSC.
If you do not have a family doctor, go to https://gap.soinsvirtuels.gouv.qc.ca/en or call 811, Option 3.
Last update: January 1, 2026
The information sheet does not replace medical advice. If you have any doubts, contact a healthcare professional.
References:
- Guides infirmiers d’éducation aux autosoins, Santé Québec Capitale-Nationale – Universitaire