Most fainting is harmless and needs nothing but the floor and a few minutes. A small proportion is the first and only warning of something that will kill the person, and the features that separate the two are simple enough to memorise.
1. What fainting is, and what it is not
A faint — syncope — is a brief loss of consciousness caused by the brain not getting enough blood for a few seconds. It ends by itself, because falling over restores the blood supply, which is why lying flat is not merely comfort but the treatment.
| It is a faint if | Think again if |
|---|---|
| Out for seconds to a minute or two, then rapidly and fully back to normal. Pale and clammy. Often a warning first | Out for more than a couple of minutes, or confused for more than about five minutes afterwards, or not fully back to their old self. That is not a simple faint and needs a different answer |
Not breathing normally is not fainting. If they are unresponsive and not breathing normally — including occasional gasping — that is a cardiac arrest, and the resuscitation chapter applies. Take a full ten seconds to decide; agonal gasps are routinely mistaken for breathing.
2. The three families of cause
| What it looks like | Typical triggers | |
|---|---|---|
| Reflex — the ordinary faint the large majority |
A warning of half a minute or so: feeling hot, nauseated, sweaty, hearing going distant, vision greying or tunnelling, yawning. Pale and clammy. Brief. Rapid full recovery | Standing still, heat, a hot bath, pain, the sight of blood, a needle, strong emotion, a long queue, coughing, straining, passing urine, standing up after a big meal |
| Orthostatic on changing position |
Happens on standing up or shortly after, sometimes with lightheadedness rather than a full faint | Medicines are the commonest cause — blood pressure tablets, diuretics, alpha blockers, nitrates, antidepressants. Also dehydration, hot weather, blood loss, alcohol, prolonged bed rest, and autonomic conditions including Parkinson's and diabetes |
| Cardiac the one that matters |
Often no warning at all — the person simply drops. May be preceded by palpitations, chest pain or breathlessness. Injury is common because there was no time to protect themselves | An abnormal rhythm, too slow or too fast; a narrowed valve; thickened heart muscle; a clot on the lung; rarely a tear in the aorta or a heart attack |
3. What to do, in order
Lie them flat and raise the legs
On the floor, on their back, legs up on a chair or held. This restores blood to the brain and it works within seconds. If they are already on the floor, leave them there.
Do not sit them up, and do not prop them against a wall
The commonest and most counterproductive thing bystanders do. Sitting someone up who has just fainted frequently makes them faint again, and this time from a height. The instinct to lift someone off the floor has to be resisted for several minutes.
Loosen anything tight, and get air moving
Collar, belt. Open a window, move the crowd back. Heat and a press of people are often part of why it happened.
Check they are breathing normally, and stay with them
If they are unresponsive and breathing, the recovery position. If not breathing normally, start CPR.
Nothing by mouth until fully alert
Then sips of water. Sugary drinks only if there is a reason to think low blood sugar and they can swallow safely.
Get them up in stages, not in one move
See the timings below. Most repeat faints happen because somebody stood up too soon.
4. How long to keep them down, and how to get them up
| Stage | How long | What you are watching for |
|---|---|---|
| Flat, legs raised | At least 10 to 15 minutes, and longer if they still feel unwell | Colour returning, sweating stopping, nausea settling, and them saying they feel normal — not merely better |
| Legs down, still flat | A couple of minutes | Any return of lightheadedness. If it comes back, legs up again and restart |
| Sitting up | 5 minutes at least, supported, with someone beside them | Pallor, sweating, greying vision. Lie them down again at the first sign |
| Standing | With someone holding them, near something to sit on | The first minute is when a second faint happens |
| Walking | Escorted, and not alone to a bathroom — which is where people faint again and hit hard surfaces | — |
Total observation before letting someone leave: roughly 30 minutes, provided they had a clear trigger, a typical warning, a rapid full recovery, no injury and no red flags. That is a working default rather than a rule. Anyone who faints again during that half hour starts the clock over and moves up the threshold for calling for help.
5. Collapsing around exercise — the commonest scenario, and the one with a trap in it
Someone training or racing who has not eaten enough, has drunk too little, and is too hot. Ears popping or hearing going oddly muffled, nausea, and then down. This is common, usually benign, and it is separated from the dangerous version by one question: was it during the effort, or after it stopped?
| After stopping — usually benign | During the effort — treat as cardiac | |
|---|---|---|
| When | At the finish line, on stopping, on standing still afterwards, in the shower, or in the queue for food | Mid-run, mid-lift, mid-match, while still working |
| Why | The leg muscles were pumping blood back to the heart. Stopping removes the pump while the vessels are still wide open from heat and exercise, so blood pools and the pressure falls | The heart could not keep up with demand — a rhythm problem, a narrowed valve, thickened muscle. The heart failing under load |
| Warning | Usually a clear one: hot, sick, hearing going distant or popping, vision greying | Often none at all |
| What to do | The sequence below | 999. And see inherited cardiac conditions afterwards, because this is how those present |
The ear popping is worth naming, because people describe it and it appears on almost no warning-sign list. As blood pressure falls, hearing changes before vision does — sounds go distant, muffled, or take on a popping or rushing quality. It is part of the prodrome, it means the same as greying vision, and it is a cue to get on the floor.
Working out which of four things it is
All four look similar at first, and the discriminator for each is simple.
| Cause | The discriminator | What it needs |
|---|---|---|
| Postural collapse after exercise the usual answer | Happened after stopping. Fully alert once flat. Recovers within minutes of lying down with the legs up | Position and time. Fluids by mouth once alert |
| Low blood sugar | Check it — below 4.0 mmol/L. Sweaty, shaky, irritable or confused, and does not improve simply from lying down | Fast-acting sugar if fully alert; 999 if drowsy. This is the one a meter settles in thirty seconds |
| Heat exhaustion, or heat stroke | Mental state is the whole distinction. Hot and unwell but lucid is exhaustion. Confused, aggressive, incoherent or not recovering is heat stroke — a 999 call and aggressive cooling. See heat illness | Cool place and fluids, or emergency cooling |
| Drinking too much plain water exercise-associated hyponatraemia | Rare, and the trap. Suspect it in long endurance events where someone has drunk large volumes of water, has not lost weight or has gained it, and is nauseated, headachy and confused rather than thirsty | 999, and do not pour more water into them. More plain fluid makes it worse, and this is the one situation where the instinct to rehydrate is actively harmful |
Recovery, for the ordinary version
Flat, legs and hips raised higher than the heart, out of the sun
Higher than for an ordinary faint if you can — this is the one situation where getting the legs well up genuinely accelerates recovery, because the problem is blood pooled in wide-open leg veins. Shade, or indoors. Loosen or remove a tight top, a race belt, a heart-rate strap.
Cool them actively while they are down
Cold wet cloths or ice to the neck, armpits and groin, and a fan or moving air. If they are confused rather than just unwell, treat it as heat stroke and call 999.
Check the glucose, and the temperature
Two readings, both fast, both capable of changing what you do next. Then pulse and blood pressure if you have a cuff.
Fluids by mouth only once fully alert
Small amounts, and something containing salt and sugar rather than plain water — an oral rehydration sachet, a sports drink, or water with a salty snack. Sips, not volume.
Ten to fifteen minutes flat, then up in the same stages as any faint
Legs down, sit, stand, walk — each with a pause and someone beside them. Most repeat collapses happen at the standing step.
No more exercise that day, and someone with them
Even if they feel fine at twenty minutes. And they should not drive home alone.
Call 999 from this scenario if
- It happened during the effort rather than after it.
- They are confused, aggressive, or not making sense — heat stroke until proven otherwise.
- They do not improve within about 15 minutes of lying flat with the legs up.
- Chest pain, palpitations or breathlessness.
- Temperature above 40 °C, or hot dry skin with confusion.
- Blood sugar below 4 and they are too drowsy to swallow safely.
- A long endurance event with a lot of plain water drunk, especially with headache, vomiting and confusion.
- Dark brown urine, or severe muscle pain and swelling in the following hours — muscle breakdown, which needs bloods and fluids.
- They banged their head. Section 9.
Afterwards, the advice is unglamorous. A single collapse after exercise in hot weather in someone who had skipped a meal and under-drunk needs no investigation if recovery was rapid and complete — but it needs the obvious fixed: eat before training, drink to thirst rather than to a schedule, acclimatise gradually to heat, and do not stop dead at the end of hard effort — walk it out for a few minutes so the leg muscles keep pumping. If it happens more than once, or during exertion at any point, that is a cardiology question and an ECG is the first step.
6. The observations, and what each one actually tells you
| Measure | What to look for | What it means |
|---|---|---|
| Blood pressure — lying, then standing | Take it lying, then again after 1 and 3 minutes of standing if they can manage it. A fall of 20 mmHg systolic or 10 mmHg diastolic within three minutes is orthostatic hypotension | Confirms the orthostatic pattern and points at medicines, dehydration or blood loss. The standing reading is the one that makes the diagnosis and the one nobody takes. See the technique chapter |
| Blood pressure — absolute | Systolic below about 90, or a big drop from their usual | Think blood loss, sepsis or a cardiac cause rather than a simple faint. A marked difference between arms with chest or back pain suggests aortic dissection — a 999 call |
| Pulse | Rate, rhythm and volume. Under 40 or over 150, or newly irregular | Points at a rhythm problem. A normal pulse afterwards excludes nothing — the arrhythmia that caused the faint has usually stopped by the time you feel the wrist, which is exactly why an ECG is needed rather than a pulse check |
| Blood glucose | Below 4.0 mmol/L | Hypoglycaemia, which is not really a faint at all — it does not resolve by lying down and it needs sugar. Thirty seconds, and it changes the management completely. See the collapse chapter |
| Temperature | Fever, or below 36 °C | Fever suggests infection and possibly sepsis, in which a faint is a warning sign rather than a nuisance. A low temperature suggests exposure or, in an older person, serious illness |
| Oxygen saturation | Below 94% on air, or breathlessness with a normal reading | Raises a clot on the lung, which classically presents as collapse with breathlessness and a normal chest examination. Read the caveats — the reading fails in exactly this situation, in a cold, shut-down patient |
| ECG, if a device is available | Rate, and whether it is regular | Useful for the handover as one line. Not a diagnosis, and it cannot exclude a cardiac cause — see single-lead ECG |
| The tongue, and the clothing | A bitten tongue — particularly the side — and wet clothing | Both point toward a seizure rather than a faint, though incontinence happens in both |
7. Call 999 if any of these
The list, and the first three are the ones to remember
- It happened during exercise or exertion. Exertional syncope is a cardiac problem until a cardiologist says otherwise. Fainting after stopping exercise is usually benign; fainting during it is not.
- It happened while lying or sitting down. A reflex faint essentially requires being upright. Losing consciousness while horizontal removes the mechanism.
- There was no warning at all. A sudden drop with no prodrome, especially with injury to the face, suggests an abrupt loss of cardiac output.
- Chest pain, breathlessness, or palpitations immediately beforehand.
- They do not recover fully and quickly, or are confused for more than about five minutes, or have any weakness, slurred speech or facial droop — which is a stroke call.
- A significant injury, especially a head injury, and especially on an anticoagulant.
- They are pregnant, or have had recent surgery, or could be bleeding — black or bloody stools, vomiting blood, severe abdominal or back pain.
- Repeated faints in a short period.
- A family history of sudden unexplained death under 40, or known heart disease. This is the flag for an inherited cardiac condition — see inherited cardiac conditions, where the trigger list includes deaths recorded as drowning or single-vehicle accidents, and where fainting during exertion or on a sudden fright appears for the same reason.
- You are worried. The last item on every list in this topic, and it is not filler.
8. Faint or seizure?
Worth being able to tell apart, because the follow-up differs entirely — and brief jerking during a faint is common and is the usual reason a simple faint gets called a fit.
| Faint | Seizure | |
|---|---|---|
| Before | Hot, nauseated, sweaty, greying vision, over about 30 seconds | Often nothing, or an odd smell, taste or rising sensation |
| Colour | Pale and clammy | May go blue or flushed |
| Movement | Brief irregular jerks, seconds, after going down | Sustained rhythmic jerking, often a minute or more, sometimes starting on one side |
| Duration | Seconds to a minute or two | Typically longer |
| Afterwards | Oriented within a minute or so | Confused, drowsy or agitated for many minutes, sometimes an hour |
| Tongue | Rarely bitten | Bitten, characteristically at the side |
The recovery is the best single discriminator. Rapid, complete reorientation points to a faint. Prolonged confusion points to a seizure — and a first seizure is a 999 call, as is any seizure over five minutes. See the collapse chapter.
9. If they banged their head on the way down
This is common, because a faint offers no time to break the fall, and a head injury sustained during a faint is assessed exactly like any other head injury.
- Apply the head injury red flags in full — head injury — including any loss of consciousness beyond the faint itself, repeated vomiting, worsening headache, drowsiness, or clear fluid from nose or ears.
- Anyone on an anticoagulant needs assessment after any head impact, however trivial and however well they appear. This is the group in which a slow bleed declares itself hours or days later, and it is the group most likely to talk themselves out of going.
- Someone must stay with them for 24 hours and be able to rouse them.
- Two problems, not one. Investigate the head injury and the reason they fainted. A head CT that comes back normal does not explain the faint, and a person discharged with the injury dealt with and the cause unexamined is at risk of the same event on a staircase.
10. Afterwards
| Situation | What should happen |
|---|---|
| A first faint, at any age | See a GP. An ECG is reasonable for anyone with unexplained syncope, and it is cheap, quick and occasionally decisive |
| A clear reflex faint with an obvious trigger, in someone who has had them before | No investigation needed. Advice on recognising the warning and preventing it — below |
| Any red flag from section 7 | Emergency assessment, and usually an ECG, bloods and cardiac review. Prolonged rhythm monitoring if nothing is found and it recurs |
| Recurrent faints without a clear pattern | Referral. Blood pressure lying and standing, a medication review, and rhythm monitoring are the useful first steps |
| Anyone who drives, or works at height or with machinery | There are legal rules and they differ by cause. A single simple faint usually carries no restriction; unexplained loss of consciousness usually does. Check the DVLA guidance and tell them — the obligation is the driver's |
Preventing the ordinary kind
- Act on the warning, immediately. The moment it starts — hot, sick, hearing going — lie down. Not "find a chair", not "get outside". Sitting is better than standing and lying is better than sitting, and on the floor in a shop is far better than falling on the way to somewhere more dignified.
- Counter-pressure manoeuvres genuinely work and are worth knowing: cross the legs and squeeze the thighs together, or grip one hand with the other and pull hard, or tense the arms. They raise blood pressure enough to abort a faint if started during the warning.
- Fluid and salt. Most reflex faints happen in someone slightly dehydrated. In people prone to them, a deliberate increase in fluid and salt intake reduces recurrence — not advice for anyone with high blood pressure, heart failure or kidney disease without asking first.
- Get up in stages after lying or sitting for a long time, and after a hot bath.
- Review the medicines. If faints started after a new tablet or a dose increase, that is the first thing to look at, and it is the commonest reversible cause in older people.
- Do not lock the bathroom door if you are prone to fainting. Unglamorous and genuinely useful.