Next-day heat exhaustion: what to know

Heat exhaustion develops when the body loses water and salts through sweating and cannot cool itself effectively. The next day, headache, dizziness, excessive thirst, dark urine, weakness, or unusual tiredness may indicate that recovery is incomplete. Heat intolerance can make another hot environment feel difficult. Symptoms may have another cause, so persistent or worsening illness should not be attributed to heat alone.

Move to a cool place, loosen unnecessary clothing, and rest. Sip water or an oral rehydration drink if you are alert and able to swallow. Avoid strenuous activity, alcohol, and more heat until you feel recovered. Eat normally if you can, and check whether urine is becoming lighter and dizziness is settling. Someone who feels faint should not be left alone.

Get emergency help for confusion, collapse, seizure, loss of consciousness, severe breathing trouble, or very hot skin with a change in mental state, because these can signal heatstroke. Seek medical care if you cannot drink, keep vomiting, remain dizzy at rest, have very dark or minimal urine, or fail to improve after cooling and fluids. Do not delay help for a vulnerable person.

Ask whether your symptoms fit heat exhaustion or dehydration, how to replace fluids safely, and when to return to exercise or outdoor work. Mention medicines or health conditions that affect sweating, fluid balance, or heat tolerance.