Stress and fainting: what should you know?

Strong emotion, fear, pain or seeing blood can activate a reflex that briefly lowers blood pressure and reduces blood flow to the brain. Standing still, heat, dehydration, missed meals and exhaustion can add to the risk. Fainting can also occur with anaemia, hypoglycaemia or an abnormal heart rhythm such as atrial fibrillation, so stress should not be assumed to be the explanation.

A warning may include nausea, sweating, warmth, blurred vision, ringing in the ears or light-headedness. Some blackouts happen without warning. The setting, posture, symptoms before the event, injury and recovery time are useful details for assessment.

If warning symptoms start, lie flat and raise your legs if possible, or sit with your head lowered. Move away from heat and ask someone to stay with you. After a blackout, rest, drink if you are fully alert and safe to swallow, and arrange medical review, especially after a first episode.

Until the cause is clear, take care around driving, heights, baths, swimming and machinery. Do not try to stand quickly after feeling faint.

Call emergency services for fainting during exercise, chest pain, severe breathlessness, palpitations, seizure-like movements, serious injury, prolonged unresponsiveness, pregnancy or a known heart condition. Urgent assessment is also needed for repeated episodes, fainting without warning or a family history of sudden cardiac death.

Ask whether blood pressure, heart rhythm, blood sugar, blood count, medicines and hydration should be checked. Describe what you were doing, how you felt beforehand, how long recovery took and whether anyone witnessed the event.