Dehydration from heat: what to know

Sweating releases heat, and hot or humid conditions can make fluid loss rapid. Headache, cramps, fatigue, dizziness, dry mouth, and dark urine may occur. Heat exhaustion can develop when sweating and salt loss continue.

Older adults, young children, outdoor workers, and people with fluid-balance conditions need extra planning. Thirst may not appear early, so regular drinks and cool breaks are useful.

Move to shade or air conditioning, loosen clothing, and cool the skin with a fan or cool wet cloth. Sip water regularly. After prolonged sweating, an oral rehydration solution may help when used as directed. Avoid alcohol and strenuous activity until recovered.

Heat exhaustion is a concern when sweating, weakness, nausea, or dizziness persists. Stay with an unwell person while they cool down.

Call emergency services for confusion, fainting, seizure, severe breathing difficulty, or someone hot who is not responding normally. Get prompt assessment for persistent vomiting, worsening weakness, inability to drink, or symptoms that do not improve after cooling. Do not give drinks to someone confused or unconscious.

Ask how to plan fluids around outdoor work, whether medicines increase heat risk, and which warning signs need urgent review.