Fainting and blacking out: what to know

People may feel warm, nauseated, light-headed, sweaty, or see spots before they black out. Standing for a long time, pain, fear, overheating, dehydration, not eating, or standing suddenly can trigger a drop in blood pressure. Some medicines and health problems can also contribute. Anaemia, dehydration, and hypoglycaemia are possible contributors, while an irregular rhythm such as Atrial Fibrillation may need consideration. Fainting itself is not a diagnosis; the circumstances and recovery pattern help a clinician work out the cause.

If someone feels faint, help them lie flat and raise their legs if there is no injury. Loosen tight clothing, provide fresh air, and do not let them stand quickly. Check that they are breathing normally. If they are unconscious, place them on their side if safe, protect the head, and do not give food or drink until fully alert. Note what happened before, during, and after the event, including medicines, food and fluids, movement, injury, and how quickly awareness returned.

Seek emergency help if consciousness does not return promptly, breathing is abnormal, there is chest pain, severe breathlessness, a racing or irregular heartbeat, a serious injury, seizure-like activity, new weakness, trouble speaking, or fainting during exercise. Arrange prompt medical review after a first blackout, repeated episodes, fainting without warning, or an episode while sitting or lying down. Until assessed, avoid driving, heights, and swimming alone.

Ask what checks may identify the cause, whether your medicines or fluid intake could play a part, and whether you need heart-rhythm monitoring or blood tests. Bring a witness account if possible and a list of medicines and supplements.