Fainting after a hot tub: what to know

Hot water raises skin temperature and can make blood pool in the legs. Standing up quickly afterward may add another drop in blood pressure. Sweating, not drinking enough, alcohol, illness or a long time in the tub can make this response stronger. Low blood sugar and heart-rhythm problems are other possibilities that need consideration, especially if the episode occurred during exertion, without warning, or more than once.

A person who faints may feel warmth, nausea, blurred vision, weakness or ringing in the ears first. These warning symptoms can stop when they lie down, but a complete blackout still deserves attention if the cause is unclear.

Get out of the water, lie flat and raise the legs if there is no injury. Turn the person on their side if they are vomiting, loosen tight clothing and keep the area cool. Do not let them return to the tub, drive or stand suddenly while recovering. Once fully awake and able to swallow, small sips of water may help; do not give drinks to someone who is drowsy.

Call emergency services if the person is not waking normally, has trouble breathing, chest pain, a severe headache, a seizure, a new irregular heartbeat, or an injury from the fall. Seek urgent assessment after fainting in the water, even if recovery seems quick, because inhaled water may cause delayed breathing problems. Arrange medical review for a first unexplained episode, repeated fainting, or fainting with known heart disease.

Ask whether your medicines, fluid balance, blood sugar, blood count or heart rhythm could have contributed. Tell the clinician how hot the water was, how long you were in it, whether alcohol was involved, what warning symptoms occurred and how quickly you recovered.