What should you know about fainting while vomiting?

Retching can activate a reflex that briefly lowers blood pressure and heart rate. Repeated vomiting may also remove fluid and electrolytes, leaving less circulating volume and making light-headedness more likely. Dehydration is therefore a useful possibility to discuss, but vomiting with fainting can have other causes, including illness, low blood sugar or anaemia.

Pay attention to blood or coffee-ground material in vomit, severe abdominal pain, fever, diarrhoea, pregnancy, new medicines and whether urine becomes unusually infrequent or dark. These details help a clinician judge urgency.

If someone collapses, place them on their side if they are breathing but may vomit again. Check breathing, remove nearby hazards and do not give food, drink or tablets until they are fully awake and can swallow normally. After recovery, use small frequent sips of an appropriate fluid rather than a large drink, which may trigger more vomiting.

Get emergency help for unconsciousness that does not quickly resolve, breathing difficulty, blue or very pale skin, severe pain, blood in vomit, a head injury, confusion, fainting during pregnancy or inability to keep fluids down. Prompt assessment is also needed after a first unexplained episode.

Ask whether you need checks for dehydration, blood sugar, anaemia or an abnormal heart rhythm. Bring a list of medicines and describe the vomiting pattern, fluid intake, urine changes and the recovery period.