Fatigue due to heat: what to know

Hot conditions make the body send more blood to the skin and produce sweat. Losing fluid and salts through sweating can leave you weak, dizzy, headachy or nauseated. Fatigue after outdoor work, exercise or time in a poorly ventilated place may improve after cooling and drinking. Dehydration can develop even before thirst feels strong.

Heat-related tiredness is different from ongoing fatigue that occurs in cool conditions or continues after recovery. Fever, infection, medication effects and other illnesses can also cause low energy. A pattern that does not settle should be assessed rather than attributed to the weather.

Move to shade or an air-conditioned room, loosen extra clothing and cool the skin with water, a fan or cool packs wrapped in cloth. Sip fluids and take a break from exertion; an oral rehydration drink may be useful after heavy sweating if it is suitable for you. Avoid alcohol while recovering, and do not return to strenuous activity until you feel well and alert.

Get urgent medical help for confusion, fainting, seizure, severe weakness, trouble breathing, chest pain, inability to drink, repeated vomiting or very hot skin with worsening symptoms. Do not leave a confused or collapsed person alone. If mild symptoms do not improve after cooling and fluids, arrange prompt medical advice.

Ask whether a medicine, illness or work environment may increase heat risk, how to replace fluids safely, and when you can resume exercise or outdoor duties.