Exhaustion and fainting

Fainting happens when the brain briefly receives too little blood flow. Standing quickly, overheating, not eating, vomiting, diarrhoea or dehydration can contribute. Anaemia can cause fatigue and light-headedness, while some medicines or heart rhythm problems need prompt assessment. The combination of symptoms does not identify a single diagnosis, so details about what happened matter.

Lie flat and raise your legs if possible, loosen tight clothing and stay still until fully alert. Turn onto your side if you are vomiting. Do not drive, climb, swim alone or operate machinery until you have been assessed. Once awake and able to swallow, take small sips of fluid and eat if you may have missed a meal. Arrange medical advice even if recovery was quick, especially after a first episode.

Call emergency services for fainting during exercise, an injury, chest pain, severe breathlessness, a pounding or irregular heartbeat, seizure-like movements, confusion, weakness on one side, difficulty speaking, severe headache, ongoing vomiting or failure to wake normally. Seek prompt clinical review for repeated episodes, fainting while lying down, pregnancy, diabetes or known heart disease.

Record your position, food and fluid intake, warning sensations, duration of unconsciousness, injuries, medicines and recovery. Ask whether blood pressure, a blood count, glucose or heart tracing should be checked, and what activity limits apply while the cause is being clarified.