Nausea and passing out: what to know

Some people feel sick, sweaty, warm, light-headed or faint before losing consciousness. Triggers can include standing for a long time, pain, fear, heat, not eating, or fluid loss from diarrhoea or vomiting. A stomach illness such as Food Poisoning or Gastroenteritis may contribute through fluid loss. Heat Exhaustion and Hypoglycaemia are other possibilities. Fainting can also have a heart or neurological cause, so the surrounding events matter: note whether there was chest discomfort, palpitations, breathlessness, injury, shaking, confusion or a long recovery.

If you feel faint, lie flat and raise your legs if you can. Loosen tight clothing, move away from heat, and do not drive. Once fully alert, take small sips of water; if you have been losing fluids, an oral rehydration drink may help. Eat a light snack if you have not eaten and can swallow safely. Someone who has fainted should be checked for breathing and injury, kept on their side if vomiting, and not given food or drink until fully awake.

Get emergency help if fainting occurs with chest pain, severe breathlessness, a pounding or irregular heartbeat, severe headache, weakness on one side, trouble speaking, serious injury, pregnancy, ongoing bleeding, or failure to regain normal awareness. Seek urgent assessment after a first unexplained episode, an episode during exercise, or repeated fainting. Arrange medical review if nausea persists, you cannot keep fluids down, or standing repeatedly brings on light-headedness.

Ask what may have triggered the episode, whether your blood pressure or blood sugar should be checked, and whether medicines, dehydration or an irregular heartbeat could be involved. Bring a timeline describing food and fluid intake, posture, warning symptoms, duration of unconsciousness and recovery.