What should you know about random fainting spells?

Before a faint, some people notice warmth, nausea, sweating, blurred vision, ringing in the ears, or weakness. A reflex spell may follow emotional distress, pain, heat, or standing still. Dehydration can follow poor fluid intake, vomiting, or diarrhoea. Low blood sugar may cause tremor, hunger, sweating, or confusion, while anaemia can be associated with persistent tiredness or breathlessness. Fainting without warning, during exertion, or alongside palpitations is more concerning because a heart rhythm disturbance can reduce blood flow suddenly. A witness account can reveal movements, skin colour, breathing, and recovery time.

At the first warning, lie down and raise your legs. If you are with someone who has fainted, place them flat, protect them from injury, and check breathing. Do not give food or drink until they are completely awake and able to swallow. Once recovered, avoid driving, bathing alone, ladders, and other hazards until assessed. Write down the trigger, body position, symptoms beforehand, medicines, recent illness, food and fluids, injury, and whether recovery was immediate or confused.

Get emergency help for fainting with chest pain, severe breathlessness, an irregular or racing heartbeat, exercise, serious injury, seizure-like activity, persistent confusion, one-sided weakness, or speech trouble. Urgent care is needed when recovery is delayed, the spell repeats, or there was no warning. Any first unexplained faint should be discussed with a clinician.

What features make this more likely to be a reflex faint or a heart-related event? Should my blood pressure, blood count, glucose, or heart rhythm be checked? Which activities should I pause?