Heat exhaustion and passing out: what to know

Heat exhaustion can reduce circulating fluid through sweating and dehydration, making it harder for the body to maintain blood flow to the brain. A person may feel faint, weak, confused, nauseated, or develop a headache before briefly losing consciousness. Passing out is not a routine symptom to watch at home because heatstroke, a heart problem, low blood sugar, or another cause can look similar. Read more about Heat Exhaustion and Dehydration.

Move the person to shade or an air-conditioned place and loosen excess clothing. Lay them flat on their back with legs raised if there is no injury and they are breathing normally. Cool the skin with wet cloths, a fan, or a cool shower. Do not give drinks, food, or medicines while the person is unconscious, vomiting, confused, or unable to swallow. Once fully awake and able to drink, offer small, frequent sips of water or an oral rehydration drink, without forcing fluids. Stay with them and avoid returning to heat or exertion.

Call emergency services if the person does not wake quickly, remains confused, has a seizure, has trouble breathing, has chest pain, or cannot drink. Seek urgent medical assessment after any heat-related loss of consciousness, even if the person seems better. Dark urine, ongoing dizziness, excessive thirst, or a severe headache also warrant prompt advice.

Ask what may have contributed to the episode, whether medicines or a medical condition increase heat risk, when normal activity is safe, and how to prevent another event during hot weather.