A common kind of faint is the simple faint, which doctors call a reflex or vasovagal faint. Blood flow to the brain drops for a short time, you pass out, and you come round quickly on your own. Common triggers include standing for a long time, getting too hot, pain, a medical procedure, being very upset, or not eating or drinking enough. Standing up too quickly can also do it, sometimes because your blood pressure falls when you stand.
The NHS says fainting is not usually a sign of something serious. NICE says the outlook after an uncomplicated faint is good. But a faint should still be checked by a GP. Some faints are caused by heart problems, and those need urgent tests. This guide explains which features matter and what happens next.
Call 112 or 999 (Ireland), 999 (UK) or 911 (US) if someone has fainted and they:
Do not drive yourself to A&E.
See a GP the same day or get urgent care if you have fainted and also have unexplained breathlessness, known heart failure or a heart murmur, or a family history of sudden cardiac death under the age of 40 or an inherited heart condition. NICE says people with these features should be referred for a heart assessment within 24 hours.
See a GP soon after any faint, even if you feel fine now.
"Syncope" is the medical word for a faint. The UK driving agency (DVLA) defines it as a brief loss of consciousness caused by reduced blood flow to the brain. It starts quickly, is short, and you recover fully on your own.
Doctors also use a wider term, "blackout", which covers faints, seizures and other causes. According to the DVLA, blackouts not caused by injury are very common, affecting up to half the UK population at some point.
Many people get warning signs first. The NHS lists dizziness, sweating, feeling warm or hot, feeling sick and changes to your vision. The NHS says a person who has fainted usually wakes up within 30 seconds.
This is the classic faint. NICE describes three features, known as the three Ps:
The NHS adds heat, and being very upset or angry, to the list of triggers. We explain what the vagus nerve does, and what online "vagus nerve hacks" can and cannot claim, in our guide to the vagus nerve.
A related type is situational syncope. NICE describes faints that are clearly and repeatedly set off by straining to pass urine (usually while standing), coughing or swallowing.
Some people faint or nearly faint when they stand up or change position. The NHS calls this postural hypotension. Symptoms include lightheadedness, blurred vision, feeling weak, confusion and fainting. The NHS defines low blood pressure as a reading below 90/60mmHg.
The NHS says low blood pressure can be normal, or linked to pregnancy, conditions such as diabetes, or some medicines. NICE notes postural hypotension is often caused or made worse by medicines. A GP can check this by measuring your blood pressure lying down and then standing up. Our article on blood pressure and the brain covers the other end of the scale.
The NHS lists not eating or drinking enough, being too hot, and taking drugs or drinking too much alcohol as causes of fainting.
NICE asks doctors to record any current medicine that may have contributed to a blackout. It gives diuretics ("water tablets") as an example. The NHS says a GP may suggest changing a medicine, or altering the dose, if it is causing low blood pressure.
If you think a medicine is making you faint, talk to your GP or pharmacist before changing anything.
The NHS lists heart problems among the causes of fainting. NICE lists these as red flags that need a heart assessment within 24 hours:
NICE also says doctors should consider the same 24-hour referral for anyone over 65 who passed out with no warning signs.
NICE says fainting during exercise makes a heart rhythm cause more likely. Fainting shortly after stopping exercise is more likely to be vasovagal. People who faint during exercise should be offered an exercise test within 7 days. NICE says they should avoid exercise until told otherwise.
The NHS also treats palpitations or chest pain with a faint, and fainting while lying down, as reasons to call 999.
It can be hard to tell, even for witnesses. Brief jerking can happen in an ordinary faint. NICE says this is common and does not by itself mean epilepsy.
Features that point towards a faint
Features that point towards a seizure
Source: NICE guideline CG109.
NICE says people with features that strongly suggest a seizure should see an epilepsy specialist within 2 weeks. Our piece on epilepsy and what actually helps explains the different seizure types.
NICE also recommends recording any future episodes, on video or with a detailed witness account, when the diagnosis is unclear.
If the room spins rather than going dark, see our guide to vertigo. Sudden face or arm weakness, or slurred speech, may be a stroke: learn the FAST signs.
NICE sets out what doctors should record after a blackout. Expect questions about:
A witness account helps, so bring someone along if you can.
NICE recommends that the check includes:
If you have a clear simple faint, NICE says no further immediate tests are needed. You should get an explanation of what happened, advice on triggers, and reassurance that the outlook is good.
If the cause is unclear or a red flag is present, you may see a heart specialist. Depending on how often episodes happen, NICE recommends:
NICE does not recommend a tilt test as a first test when a heart rhythm cause is suspected. It also says an EEG (brainwave test) should not be used routinely for blackouts.
UK. NICE says anyone who has had a blackout must not drive while waiting for a specialist assessment. The NHS says you must not drive if your GP has referred you to a specialist and you are waiting to be seen. For car and motorcycle drivers, DVLA medical guidance (updated 7 November 2025) says:
Different, stricter rules apply to bus and lorry drivers, to cough syncope, and to faints without warning signs. GOV.UK says you can be fined up to £1,000 if you do not tell DVLA about a condition that affects your driving.
Ireland. The Irish guidelines, Sláinte agus Tiomáint (April 2026), say people with symptoms such as blackouts should be advised not to drive until they have been properly assessed. During that period no formal contact with the NDLS is needed. Once a diagnosis is clear, the normal notification rules apply. The HSE says you must tell the NDLS if you are fainting regularly. The RSA says you must tell the NDLS and your insurer about any long-term illness that may affect your ability to drive safely.
US. Rules differ, and we have not covered them here. Ask your doctor.
If you feel faint, the NHS suggests you:
The HSE also suggests eating something and taking some deep breaths.
If standing up is the trigger, the NHS suggests getting up slowly, drinking more water, eating small, frequent meals and limiting alcohol. If you are unsure what sets your faints off, NICE suggests keeping a record of when they happen and what you were doing.
Yes. The NHS advises seeing a GP after a faint. It is probably nothing serious, but a GP can check for causes such as low blood pressure or a heart problem. Call 999 or 112 instead if any of the warning signs in the box above apply.
Medical procedures and pain are classic triggers for reflex faints. Tell the person taking blood beforehand. Lying down for the test may help. NICE notes that episodes prevented by lying down point towards a simple faint.
Being very upset is a recognised trigger for a simple faint. Sometimes episodes that look like blackouts are not faints or epileptic seizures. NICE asks doctors to consider this if the episodes change over time, last unusually long, or come with many unexplained physical symptoms. That needs a neurology assessment, not a guess. The NHS also lists feeling faint among the symptoms of a panic attack. Our guide to panic attacks and panic disorder explains the difference.
Not necessarily. NICE says brief jerking is common in ordinary faints. The features in the list above help tell them apart, so tell your GP exactly what witnesses saw.
This article is general information, not medical advice. It cannot diagnose the cause of a faint. If you have fainted, see your GP, or call emergency services if any warning signs apply.
Reviewed by: Proco Team
Last updated: November 2026