What should you know about blackout spells?

A blackout spell is a temporary loss of awareness that should be assessed when its cause is uncertain. Fainting often happens when blood flow to the brain briefly falls, while other episodes may relate to heart rhythm, blood sugar, dehydration, or neurological activity. The setting, warning symptoms, body movements, injuries, and speed of recovery all help guide the next step.

A spell after standing for a long time, heat, pain, fear, or a missed meal may suggest a fainting trigger. Light-headedness, sweating, nausea, and narrowing vision can occur beforehand. Sudden collapse without warning, palpitations, exertional symptoms, or confusion after waking needs particular attention. Anaemia, dehydration, hypoglycaemia, and atrial fibrillation can present with blackouts, but the presence of a blackout does not identify which condition is responsible.

If warning symptoms begin, sit or lie down immediately and raise your legs if comfortable. If someone has collapsed, check breathing, clear hazards, and place them on their side when appropriate. Do not give drinks until they are awake and able to swallow. Write down the trigger, posture, food and fluid intake, medicines, duration, and any movements or injury. A witness account is often useful.

Seek emergency help for ongoing unresponsiveness, breathing difficulty, severe injury, repeated spells, chest pain, or a racing or irregular heartbeat. Treat a blackout during exercise, while driving, or without warning as urgent. A first episode, a new pattern, or a spell in someone with heart disease warrants prompt medical review even when the person feels well again.

Ask what causes are most relevant to your pattern, whether heart monitoring or blood tests are needed, and how to reduce risk while the assessment is underway. Check whether any medicine, fasting pattern, heat exposure, or fluid loss could be contributing.