Post-prandial syncope: what should you know?

After a meal, digestion changes blood flow and blood pressure. Some people become light-headed when the body does not compensate adequately, particularly after a large meal, standing quickly, heat exposure or not drinking enough. Low blood glucose, anaemia, an irregular heart rhythm and dehydration can also contribute. These possibilities do not mean that any one condition is present; the pattern and examination matter.

Tell a clinician whether you fully lost consciousness, how soon after eating it happened, what you ate and drank, and whether there was chest discomfort, racing heartbeat, sweating or shaking. A medication review, blood pressure checks and selected tests may help clarify the cause.

At the first warning of faintness, sit or lie down in a safe place and raise your legs if possible. Do not drive, climb or bathe alone until the episode has been discussed with a clinician. Keep a record of meals, fluids, symptoms, posture and medicines. Regular fluids and smaller meals may help some people, but do not change diabetes or blood-pressure treatment without advice.

Seek emergency help for fainting with chest pain, severe breathlessness, a new neurological problem, a serious injury, prolonged confusion or an ongoing seizure. Prompt medical review is also needed if episodes recur, happen during exertion, occur without warning or affect someone with known heart disease.

Ask whether your symptoms fit a blood-pressure change after meals, whether medicines or glucose levels need review, and which activities should be avoided until the cause is clearer.