Fainting after standing up: what to know

When you rise, gravity draws blood toward the legs. The body normally tightens blood vessels and adjusts the heart rate to keep blood reaching the brain. Dehydration, prolonged bed rest, heat, illness and some medicines can make that adjustment slower. Anaemia and low blood sugar can also cause weakness or light-headedness, so the trigger alone does not establish the cause.

Warning signs may include greying vision, nausea, sweating, weakness or a feeling that the room is moving. Sitting or lying down at the first sign can prevent a fall.

If dizziness starts, sit or lie down immediately and avoid walking until it passes. Rise in stages: turn onto your side, sit at the edge of the bed, move your ankles, then stand while holding a stable surface. Drink regularly unless a clinician has limited your fluids, and review medicines with a professional rather than stopping them yourself.

Get emergency help for fainting with chest pain, breathing difficulty, a new irregular heartbeat, seizure-like movements, severe headache, injury, persistent confusion or trouble speaking. Arrange a medical appointment if episodes recur, occur without warning, happen while lying down, or began after a medicine change. Blood pressure lying and standing can help identify the pattern.

Ask whether your medicines, hydration, blood count, glucose level or heart rhythm should be checked. Bring a record of posture, time of day, meals, symptoms, falls and how long recovery took.