What should you know about fainting while sitting down?

Fainting, also called syncope, happens when the brain briefly receives too little blood flow. Sitting does not remove every possible trigger. Dehydration, missed meals, anaemia, illness or a sudden fall in blood pressure can contribute. A heart rhythm problem can also reduce blood flow without warning; Atrial Fibrillation is one condition a clinician may consider, although this symptom alone cannot identify its cause.

Record what happened just before the event, including posture, palpitations, chest discomfort, sweating, nausea, food and fluid intake. A witness can describe colour change, movements, breathing and how quickly normal awareness returned.

If warning symptoms return, lie flat and raise your legs if there is no injury. Loosen tight clothing, keep the area clear and do not stand suddenly. Once fully alert, take small sips of fluid if swallowing is safe. Do not drive, climb or bathe alone until the episode has been assessed.

Call emergency services if the person remains unconscious, has trouble breathing, severe chest pain, a new irregular heartbeat, one-sided weakness, trouble speaking, a serious injury or prolonged confusion. Seek prompt medical care after any unexplained seated faint, particularly when it happens during exertion or without warning.

Ask whether you need an examination, blood tests, an electrocardiogram or monitoring of your heart rhythm. Discuss whether dehydration, low blood sugar or anaemia could be relevant, and which warning signs should change your action plan.