Severe heat exhaustion: what to know

Heat exhaustion occurs when the body loses fluid and salt through sweating faster than they are replaced, especially during hot weather, exertion, or poor acclimatisation. Signs can include heavy sweating, weakness, headache, dizziness, nausea, muscle cramps, thirst, cool clammy skin, and dark urine. Dehydration can accompany or worsen the illness. Heat intolerance may increase vulnerability, but symptoms can progress quickly, so the person's alertness and response to cooling matter more than trying to name the condition at home.

Move the person to shade or an air-conditioned place. Have them lie or sit comfortably, loosen excess clothing, and cool the skin with a fan, cool wet cloths, or a cool shower. If they are awake and able to swallow, offer frequent small sips of water or an oral rehydration drink. Stop activity and stay with them while monitoring alertness. Do not give drinks to someone who is confused, vomiting repeatedly, having a seizure, or unable to swallow safely.

Call emergency services immediately for confusion, unusual behaviour, loss of consciousness, seizure, very hot skin, severe breathing difficulty, or inability to drink. Seek urgent medical care if symptoms are severe, worsen, or do not clearly improve after cooling and rest. A person who remains weak, dizzy, repeatedly vomits, or passes very dark urine may need assessment and supervised rehydration. Children, older adults, pregnant people, and people with chronic illness need a lower threshold for help.

Ask what caused the episode, how to return safely to activity, and whether medicines or a health condition affect heat tolerance. Discuss a hydration and cooling plan before working or exercising in hot conditions.