Fainting after vomiting: what to know

Vomiting can remove fluid and salts, making it harder to maintain blood pressure. The act of retching can also activate a reflex that briefly changes heart rate and blood-vessel tone. Pain, fever, heat, standing, not eating and alcohol may add to the strain. Warning symptoms can include clamminess, ringing in the ears, nausea, dim vision or sudden weakness.

Fainting is not a diagnosis by itself. Dehydration, low blood sugar, Anaemia, an abnormal heart rhythm such as Atrial Fibrillation, medication effects or bleeding can be involved. The cause is more concerning when vomiting is persistent, the faint happened without warning, or there was chest discomfort or a racing heartbeat.

Lie flat with your legs raised if comfortable, and turn onto your side if vomiting continues. Stay with the person until they are fully awake. Once alert and able to swallow, take small frequent sips of an appropriate rehydration drink; stop if this triggers more vomiting. Avoid standing suddenly, driving or bathing alone until reviewed.

Do not give anything by mouth to someone who is drowsy or unconscious. Note the number of vomiting episodes, fluid intake, medicines, blood in vomit or stool, and the duration of unconsciousness. This information helps a clinician judge fluid loss and other causes.

Get emergency help if consciousness does not return promptly, breathing is abnormal, there is chest pain, severe abdominal pain, a severe headache, new weakness, seizure-like movement, confusion or a significant head injury. Blood or coffee-ground material in vomit, black stool, or inability to keep fluids down also needs urgent attention.

Arrange prompt review after a first faint, any recurrence, or symptoms of marked Dehydration or Hypoglycaemia. Do not assume vomiting explains the event if it occurred during exercise or without warning.

Ask whether you need blood pressure checks, an ECG, blood tests or treatment for fluid and salt loss. Tell the clinician about diarrhoea, fever, pregnancy possibility, diabetes medicines, bleeding, palpitations and any family history of heart problems.