Fatigue in hot weather: what to know

Heat makes the body work harder to control its temperature. Blood flow shifts towards the skin and sweating removes water and salts. The result may be low energy, thirst, headache, dizziness, nausea, cramps or a faster heartbeat. Hot, poorly ventilated rooms and exercise increase the load, while alcohol can make fluid loss and sleep disruption worse.

If tiredness continues after you cool down, consider other causes. Anaemia, COVID-19, coeliac disease, burnout and chronic fatigue syndrome can present with fatigue; chronic kidney disease may also affect energy and fluid handling. Symptoms do not identify one diagnosis by themselves.

Pause strenuous activity and move to shade or air conditioning. Drink small, regular amounts of water, cool your skin with a damp cloth, and wear loose, breathable clothing. Take breaks before you feel exhausted, avoid alcohol during recovery, and plan exercise for cooler hours. People with kidney or heart conditions should ask their clinician how much fluid is appropriate rather than changing intake substantially.

Emergency help is needed for confusion, collapse, seizure, severe drowsiness, inability to drink or rapidly worsening illness in the heat. Seek prompt advice if vomiting, faintness, weakness, headache or a racing heartbeat does not settle after cooling and fluids. Arrange a review when fatigue persists in air-conditioned settings, repeatedly returns or affects work, sleep or daily tasks.

Ask whether your medicines, kidney function, blood count, recent infection, sleep, mood or alcohol use could be contributing. Describe heat exposure, sweating, urine changes, fluid intake and how quickly symptoms improve indoors.