Orthostatic vasovagal syncope: what to know

A vasovagal reflex can slow the heart and widen blood vessels, while standing allows blood to pool in the legs. Together, these changes can reduce blood flow to the brain briefly and cause light-headedness or fainting. Warm rooms, prolonged standing, pain, fear, dehydration, and missed meals may act as triggers. A clinician still needs to consider other causes, including anaemia, low blood sugar, dehydration, or an abnormal heart rhythm.

At the first warning—such as nausea, sweating, blurred vision, warmth, or ringing in the ears—lie flat and raise your legs if possible. If lying down is not practical, sit and lower your head. Once recovered, stand slowly and avoid driving or climbing until you have medical advice. Regular fluids and meals may help when appropriate. Leg crossing and tensing the leg and arm muscles can support blood flow while standing.

Book a medical assessment after a first faint or repeated near-faints so the circumstances and medicines can be reviewed. Seek urgent help for chest discomfort, breathlessness, fainting during exertion, palpitations, severe injury, prolonged confusion, or a slow recovery. Do not assume a vasovagal explanation when the event is sudden, occurs without warning, or happens while lying down.

Ask which triggers fit your episode, whether you need an upright blood-pressure check or heart tracing, and whether your fluid or salt intake needs individual advice. Clarify when you can return to driving, exercise, work at height, or water-related activities.