Heat fatigue symptoms: what to know

Heat makes the body send more blood to the skin and lose fluid through sweat. That can leave you drained, light-headed or less able to focus, especially after exercise, outdoor work or time in a hot room. Muscle cramps, nausea and a fast heartbeat may also occur. Fatigue that continues after cooling and drinking needs assessment because dehydration and illnesses such as anaemia, COVID-19 or kidney disease can also cause low energy.

Stop strenuous activity and move to shade or an air-conditioned place. Loosen extra clothing, cool your skin with a damp cloth, and take frequent small sips of water; an oral rehydration drink may help after substantial sweating. Rest until your alertness and strength improve. Avoid alcohol and return to activity gradually. If symptoms recur, note the heat, activity, fluids and medicines involved, then arrange a clinical review.

Seek emergency help for confusion, fainting, a seizure, severe breathing trouble, inability to drink, or skin that feels very hot with worsening illness. Get prompt medical advice if vomiting prevents fluids, symptoms are worsening, or you remain markedly weak after cooling. A clinician can check hydration and consider causes such as dehydration, burnout or chronic fatigue syndrome.

Ask whether your pattern fits heat illness, whether medicines or another condition may impair sweating, and which fluids and activity limits are suitable for you. Mention fever, weight change, sleep problems, heavy periods, bowel symptoms or reduced urination.