Syncope (fainting): symptoms, causes, tests and treatment

The NHS describes fainting as passing out for a short time. It says fainting is not usually a sign of something serious, but anyone who has fainted should see a GP. NICE Clinical Knowledge Summaries describe a blackout as a transient loss of consciousness, with syncope being the version caused by a temporary shortage of blood flow to the brain.

Other conditions can look like fainting. NICE CKS lists epilepsy or seizure and psychogenic pseudosyncope or non-epileptic seizures as non-syncopal causes of blackout. Telling these apart is a central part of the assessment, which is why an account from a witness matters.

The NHS says fainting usually happens suddenly. Symptoms that can come before it include dizziness, sweating, feeling warm or hot, feeling sick and changes to your vision. NICE CKS refers to these as prodromal symptoms and says that recognising them early is part of the management of reflex syncope.

If you notice them, the NHS advice is to lie down with your legs raised, or if you cannot, sit with your head lowered between your knees. Afterwards, anyone who has fainted should see a GP even if they feel fine.

• Dizziness or light-headedness

• Sweating

• Feeling warm or hot

• Feeling sick

• Changes to your vision

NICE CKS divides syncope into three main groups. Reflex or neurally mediated syncope includes vasovagal faints, situational faints (for example with coughing or passing urine) and carotid sinus syndrome. Orthostatic hypotension means blood pressure falls on standing. Cardiac syncope is caused by a heart rhythm problem or a structural heart condition.

The NHS lists everyday triggers: standing up too quickly, not eating or drinking enough, being too hot, being very upset, angry or in severe pain, heart problems, and drugs or too much alcohol.

Possible warning symptoms before a faint include dizziness, sweating, feeling warm or hot, feeling sick and changes to vision, according to the NHS.

The NHS says call 999 if the person is not breathing, cannot be woken within 1 minute, has not fully recovered or has difficulty with speech or movement, has chest pain or a pounding, fluttering or irregular heartbeat, has seriously hurt themselves before or after fainting, is shaking or jerking, fainted while exercising, or fainted while lying down. Do not drive yourself to A&E.

For anyone else who has fainted, the NHS says to see a GP. NICE CKS asks clinicians to take a detailed history, including any history or family history of cardiac disease or sudden death, and says to consider specialist referral for unexplained syncope or reflex syncope with an absent or short warning.

The NHS advises that if you feel you are about to faint you should lie down with your legs raised, or sit with your head lowered between your knees. Drinking some water, crossing your legs while standing, rocking up and down on your toes and clenching your fists can also help.

If you see someone faint, check they respond by gently shaking their shoulders and asking if they are all right. If not, shout for help, tilt the head back and lift the chin, and listen for breathing for at least 10 seconds. If they are breathing normally, lay them on their back and raise their legs. If they are pregnant, especially beyond 28 weeks, lay them on their side. The NHS says most people wake within 30 seconds.

NICE CKS says assessment includes vital signs, lying and standing blood pressure (standing for at least 1 minute), a blood glucose level, and a cardiac and neurological examination. The clinician asks the person and any first-hand witness about the circumstances of the event: posture beforehand, any warning symptoms, appearance, movement or injury during the event, tongue-biting or loss of bladder or bowel control, how long it lasted, any confusion afterwards, any triggers, previous episodes and family history.

A 12-lead ECG is arranged, with further tests such as blood tests, 24-hour ambulatory blood pressure monitoring or an echocardiogram depending on clinical judgement. NICE CKS also suggests that the person or carer makes a video recording of future events.

Treatment depends on the cause. NICE CKS says management includes education and advice on sources of information and support, advice on fitness to drive and safety at work, and referral to an appropriate specialist if there is a suspected cardiac cause, carotid sinus syndrome or epilepsy.

For suspected reflex syncope or orthostatic hypotension, NICE CKS advises on triggers, early recognition of warning symptoms and lifestyle changes such as adequate fluids and physical counter-pressure manoeuvres, and reviewing drug treatment. For orthostatic hypotension it lists further measures such as small frequent meals, drinking a fluid bolus, dietary salt supplementation, regular physical activity, head-up tilt sleeping and compression garments.

The NHS says you must tell the Driver and Vehicle Licensing Agency (DVLA) if you are fainting regularly, as it could affect your ability to drive. You must not drive if your GP has referred you to a specialist and you are waiting to be assessed.

NICE CKS lists possible complications as injury and falls, loss of confidence, anxiety and depression, and effects on work, study and driving. Management therefore includes advice on fitness to drive and safety at work, and on triggers and early recognition of warning symptoms.

NICE CKS suggests referral to a falls and syncope service or cardiologist if there is diagnostic uncertainty, unexplained syncope, vasovagal syncope during a high-risk activity or affecting quality of life, reflex syncope with a short or absent warning, suspected but unconfirmed orthostatic hypotension, or orthostatic hypotension that persists despite lifestyle changes.

Private cardiology is another route to tests such as an echocardiogram or heart rhythm monitoring. Share the findings with your GP, because any driving advice and medicine changes sit with them.