What should you know about sudden fainting?

Fainting, or syncope, happens when the brain briefly receives too little blood flow. Some people feel warm, nauseated, sweaty, light-headed or see spots before they collapse. Standing quickly, pain, fear, dehydration, anaemia, hypoglycaemia and some medicines can contribute. Atrial fibrillation and other rhythm problems can also cause collapse, sometimes without warning. The event itself does not identify its cause.

Ask someone who saw it to describe your colour, movements, breathing, duration and recovery. Injuries, exertion, palpitations, chest discomfort and a family history of sudden heart problems are important details.

If you feel faint, lie flat and raise your legs if possible, or sit with your head lowered. Loosen tight clothing and move away from heat. After a collapse, check breathing and responsiveness; call emergency services if the person does not wake promptly or is injured. Do not give food or drink until fully alert. Arrange medical review after any unexplained faint, even if recovery feels complete.

Call emergency services for fainting during exercise, chest pain, breathlessness, a racing or irregular heartbeat, severe injury, seizure-like activity, prolonged confusion, pregnancy, or new weakness or speech trouble. Emergency assessment is also needed when fainting occurs without warning or while lying down. Repeated episodes require prompt review.

Ask whether you need an ECG, blood tests or blood-pressure checks, and whether dehydration, blood sugar, anaemia or a rhythm problem could explain the event. Discuss warning symptoms and how to reduce falls while the cause is being assessed.