What should you know about vasomotor syncope?

A trigger such as prolonged standing, heat, emotional distress, pain or seeing blood can activate the body's automatic nerves. Heart rate and blood vessel tightening may briefly change, so less blood reaches the brain. Before losing consciousness, you may feel warm, nauseated, light-headed, sweaty or notice dimming vision. Recovery often begins after lying flat, but tiredness can linger.

A faint can also have other explanations. Dehydration, anaemia, low blood sugar and abnormal heart rhythms may produce similar symptoms, so the circumstances matter. A clinician may ask about the trigger, posture, medicines, injuries and family history.

At the first warning, lie down and raise your legs if possible. If you cannot lie down, sit and lower your head between your knees. Loosen tight clothing, move away from heat and do not stand quickly when you start to feel better. Someone who has fainted should be placed on their back with the airway clear and monitored while they recover.

Keep a record of what happened, including food and fluids, posture, warning symptoms and how long recovery took. Regular fluids and avoiding known triggers may help, but salt changes or compression garments should be discussed with a clinician, especially if you have heart or kidney problems.

Seek urgent help if fainting happens during exercise, causes a serious injury, occurs with chest pain, breathlessness, a racing or irregular heartbeat, seizure-like movements, prolonged confusion or difficulty speaking. Urgent assessment is also needed if the person is not breathing normally or does not promptly regain consciousness.

Arrange a medical review after a first faint, repeated episodes, fainting without warning, or a faint while sitting or lying down. Assessment can help separate a reflex faint from dehydration, anaemia or a heart rhythm problem.

Ask what trigger pattern fits your episode, whether your medicines or fluid intake could contribute, how to recognise your personal warning signs, and whether you need an ECG or other checks before returning to driving, work at height or swimming alone.