What should you know about repeated fainting?

Repeated fainting needs medical assessment because it can result from dehydration, low blood sugar, anaemia, or a heart-rhythm problem. Fainting, also called syncope, happens when the brain briefly receives too little blood flow, leading to a short loss of consciousness. A clinician will want to know what you were doing, how quickly you recovered, whether you were injured, and whether you felt warning symptoms beforehand.

A reflex faint may follow standing for a long time, heat, emotional stress, pain or seeing blood. A drop in blood pressure after standing can also reduce brain blood flow. Dehydration can present with fainting, especially when fluid loss has followed vomiting, diarrhoea, fever or heavy sweating. Anaemia can present with fainting alongside tiredness, breathlessness or a fast heartbeat. Hypoglycaemia can present with fainting and may also cause sweating, shaking, hunger or confusion. An abnormal heart rhythm, including atrial fibrillation, can present with fainting or near-fainting and palpitations. These possibilities cannot be distinguished safely from the faint alone.

If you feel faint, lie down and raise your legs if you can. If lying down is not possible, sit and lower your head between your knees. Loosen tight clothing, move away from heat and ask someone to stay with you. Do not drive, climb or operate machinery until you have been assessed. Arrange a prompt medical appointment after repeated episodes, even if you feel well between them. Record triggers, posture, warning symptoms, food and fluid intake, medicines, injuries and the time needed to recover. A witness can describe movements, skin colour and responsiveness, which helps distinguish fainting from other causes of collapse.

Seek emergency help if someone does not wake promptly, has trouble breathing, has chest pain, develops severe headache or weakness, has a prolonged seizure-like episode, or remains confused. Urgent assessment is also needed when fainting happens during exercise, while lying down, after a strong heartbeat sensation, or with a significant injury. Do not give food or drink to an unconscious person. Place a breathing person on their side if they are not fully alert, and check that help has been called.

Ask what examinations or tests could clarify the cause, whether any medicine or supplement might contribute, and which activities should be avoided until the evaluation is complete. Tell the clinician about family history of sudden cardiac death, heart disease, bleeding, heavy periods, diabetes, recent illness and any new treatment. Bring an episode diary and, if available, a witness account.