Nausea after fainting: what to know

A vasovagal episode can cause warning symptoms such as nausea, sweating, warmth, blurred vision and light-headedness before consciousness is lost. Nausea may linger while circulation settles. Dehydration, overheating, standing for a long time, pain, emotional stress or low blood sugar can contribute. Anaemia can reduce oxygen delivery and atrial fibrillation or another heart rhythm problem can affect blood flow, so the context matters. Fainting during exertion, while lying down, or with palpitations deserves particular attention.

Lie flat with your legs raised if there is no injury and you can breathe comfortably. Turn onto your side if vomiting or not fully alert, and do not stand suddenly. Once fully awake, take small sips of fluid and eat a light snack if low blood sugar may have contributed and swallowing is safe. Avoid driving, heights and swimming until a clinician has advised you. Write down what happened before, during and after the faint, including medicines and witnesses' observations.

Call emergency services for prolonged unresponsiveness, trouble breathing, chest pain, a severe headache, new weakness, confusion, a serious injury, seizure-like movements, fainting during exercise, or repeated fainting. Seek urgent assessment for black or bloody stool, heavy bleeding, persistent vomiting or signs of severe dehydration. Arrange a medical appointment after any unexplained faint, even if nausea settles; an examination, blood pressure check, blood tests or heart tracing may be needed.

What might have triggered the faint? Do I need a heart rhythm check, blood test or medication review? When is it safe to drive and return to exercise?