Heat exhaustion: what to know and do

Heat exhaustion can follow prolonged heat, strenuous activity, or work in a hot and humid environment. Sweating removes water and salts, and the body may struggle to keep its temperature controlled. People may feel weak, light-headed, nauseated, thirsty, or develop a headache. Skin is often cool or clammy with heavy sweating, though presentation varies.

Dark urine, reduced urination, excessive thirst, and dizziness can point to dehydration alongside heat illness. Heat intolerance, medicines, age, pregnancy, and some long-term conditions can increase vulnerability. Heat exhaustion can progress to heat stroke, especially if the person remains in the heat or cannot drink.

Stop activity and move to a cool, shaded, or air-conditioned place. Remove unnecessary outer clothing, loosen tight clothing, and cool the skin with wet cloths, fans, or a cool shower. If the person is awake and able to swallow, give frequent small sips of cool water or an oral rehydration drink.

Rest and continue cooling until symptoms improve. Avoid alcohol and strenuous activity while recovering. Do not leave a confused, very weak, or vomiting person alone, and do not force fluids if swallowing is unsafe.

Call emergency services if the person becomes confused, faints, has a seizure, cannot drink, keeps vomiting, develops very hot skin, or does not improve promptly with cooling. These signs may indicate heat stroke, which needs emergency treatment.

Arrange medical advice if symptoms recur, dehydration signs continue, or the person has a condition or takes medicine that affects fluid balance. Keep cooling measures going while help is arranged.

Ask whether dehydration contributed, how to return to exercise or outdoor work, whether your medicines increase heat risk, and which early symptoms should trigger a cooling break.