Can dehydration cause heat exhaustion?

Heat exhaustion develops when heat exposure and exertion place more demand on cooling than the body can manage. Sweating removes water and salts, and dehydration leaves less fluid available for sweating and circulation. Symptoms may include heavy sweating, weakness, headache, dizziness, nausea, thirst, cool clammy skin, and a fast pulse. Heat, humidity, tight clothing, illness, and strenuous activity can all add to the strain.

Stop exertion and move into shade or an air-conditioned place. Lie down or sit with support, loosen clothing, and cool the skin with wet cloths, a fan, or cool water. If you are awake and able to swallow, take small frequent sips of water or a suitable rehydration drink. Stay with the person and watch for changes. Do not resume activity until fully recovered and avoid alcohol while rehydrating.

Seek urgent help if there is confusion, unusual behaviour, fainting, a seizure, loss of consciousness, severe breathlessness, or inability to drink. Very hot skin or symptoms that worsen or fail to improve after cooling require urgent assessment. Do not give drinks to someone who is confused or cannot swallow safely.

Ask how to plan fluids and breaks for work, sport, or outdoor time, and whether medicines or health conditions increase your heat risk. Discuss any episode that recurs or takes a long time to settle.