Fainting, Heart Problems and Epilepsy Lookalikes
Why collapse, stiffening or jerking does not automatically mean epilepsy
Someone suddenly collapses.
Their eyes may be open.
Their body may stiffen.
Their arms or legs may jerk.
They may make a strange sound.
For witnesses, this can look exactly like an epileptic seizure.
But epilepsy is not the only condition capable of producing this appearance.
One of the most important alternatives is syncope — fainting caused by a temporary reduction in blood flow to the brain.
Some cardiac rhythm disorders can also cause sudden loss of consciousness and may occasionally produce seizure-like movements.
NICE specifically warns that brief seizure-like activity can occur during an uncomplicated faint and does not necessarily mean the person has epilepsy.
This is why assessment after a blackout should consider both:
the brain
and the heart.
What does “blackout” mean?
The medical term transient loss of consciousness — TLoC is often used when someone temporarily loses consciousness and then recovers.
A blackout describes what happened.
It does not explain why it happened.
Possible causes include:
epileptic seizures
vasovagal syncope
postural hypotension
cardiac arrhythmias
structural heart disease
situational syncope
functional events
metabolic problems
and other medical conditions.
The first job is therefore not:
“Which type of epilepsy is this?”
It is:
“What caused the loss of consciousness?”
NICE recommends taking a detailed account from the person and witnesses, including what happened before, during and after the event.
What is syncope?
Syncope means a temporary loss of consciousness caused by inadequate blood flow to the brain.
It usually has:
rapid onset
relatively short duration
and spontaneous recovery.
The underlying mechanisms vary.
Major categories include:
reflex or vasovagal syncope
postural or orthostatic hypotension
and cardiovascular causes such as abnormal heart rhythms or structural heart disease.
What is vasovagal syncope?
Vasovagal syncope is the common faint.
A reflex causes:
blood pressure to fall
and sometimes heart rate to fall as well.
As a result, blood flow to the brain temporarily becomes insufficient and the person loses consciousness.
NHS specialist services describe common warning symptoms including:
dizziness
sweating
nausea
feeling weak
blurred vision
hearing becoming distant
and pallor.
The three Ps of an uncomplicated faint
NICE uses three useful clues when assessing uncomplicated vasovagal fainting.
Posture
For example:
prolonged standing
or previous episodes that improve when the person lies down.
Provoking factors
Such as:
pain
medical procedures
needles
or seeing blood.
Prodromal symptoms
Such as:
sweating
feeling warm
nausea
or light-headedness.
When this typical pattern is present and there are no concerning alternative features, an uncomplicated faint may be diagnosed clinically.
What does fainting feel like before consciousness is lost?
People may describe:
dizziness
light-headedness
nausea
sweating
feeling hot
weakness
grey or narrowing vision
blurred vision
sounds becoming distant
ringing in the ears
or an overwhelming feeling that they need to sit or lie down.
Someone who recognises these symptoms may sometimes prevent complete loss of consciousness by lying down.
That pattern can be diagnostically useful.
Why does lying down help a faint?
Gravity contributes to blood pooling in the lower body while standing.
Lying flat makes it easier for blood to return to the heart and brain.
NICE specifically notes that symptoms which have previously been abolished by sitting or lying down make epilepsy less likely when investigating transient loss of consciousness.
This does not mean every event that improves on sitting is definitely a faint.
It is one clue among several.
Can fainting cause jerking?
Yes.
This is one of the biggest sources of confusion.
When blood flow to the brain becomes sufficiently reduced during syncope, the person may develop brief abnormal movements.
These can include:
stiffening
jerks of the arms or legs
eye movements
brief twitching
or other seizure-like activity.
NICE explicitly states that brief seizure-like activity can often occur during uncomplicated faints.
So the rule:
“They shook, therefore it was epilepsy”
is medically unreliable.
What is convulsive syncope?
The term convulsive syncope is used when fainting is accompanied by seizure-like motor activity.
The underlying problem remains a temporary loss of cerebral blood flow rather than an epileptic discharge beginning in the brain.
The person may:
collapse
stiffen
jerk
make sounds
and appear very similar to somebody having a convulsive epileptic seizure.
Abnormal heart rhythm is one recognised cause of seizure-like syncope. Epilepsy Action lists arrhythmia with convulsive syncope among non-epileptic causes of seizure-like events.
The movements themselves may not settle the diagnosis
Neurologists and cardiologists therefore look beyond:
“Was there shaking?”
They ask:
what happened before the collapse
how the person looked
how long the movements lasted
whether there was head turning
whether there was unusual posturing
what happened immediately afterwards
and whether there were cardiovascular warning signs.
The complete sequence is more useful than one visible feature.
Features that make epilepsy more likely
NICE identifies several features that are strongly suggestive of an epileptic seizure following transient loss of consciousness.
These include:
bitten tongue
head turning to one side
no memory of abnormal behaviour witnessed by someone else
unusual posturing
prolonged limb jerking
confusion after the event
and déjà vu or jamais vu before the event.
These features should prompt urgent specialist epilepsy assessment.
They are clues rather than standalone diagnostic tests.
Features that may make epilepsy less likely
NICE says an episode may be less likely to represent epilepsy when there is:
sweating before the event
prolonged standing that appears to precipitate it
pallor during the episode
or preceding symptoms that have previously been prevented by sitting or lying down.
Again, no single feature decides the diagnosis.
Several features need to be interpreted together.
Colour can be useful
A witness may notice that someone becomes:
very pale
flushed
grey
or blue.
NICE specifically recommends recording the person's complexion during transient loss of consciousness.
Pallor can support syncope in the correct clinical setting.
But colour change alone is not diagnostic.
Recovery can be informative
People with uncomplicated syncope often regain consciousness relatively quickly once normal blood flow returns.
They may still feel:
weak
nauseated
tired
or washed out.
By contrast, some epileptic seizures are followed by a more characteristic postictal state, with:
confusion
memory loss
deep sleep
language difficulty
or prolonged disorientation.
NICE specifically lists confusion following the event as a feature strongly suggestive of epilepsy.
But recovery patterns overlap.
Rapid recovery does not prove syncope, and tiredness does not prove epilepsy.
Fainting is not always harmless
Many faints are uncomplicated vasovagal syncope.
But some blackouts are caused by potentially serious cardiovascular disease.
That is why a blackout should not simply be labelled:
“just a faint”
without considering the context.
Cardiac causes can include:
abnormal heart rhythms
heart conduction disorders
structural heart disease
inherited cardiac conditions
and other problems reducing blood flow from the heart.
Why the heart can cause seizure-like events
The brain depends continuously on blood containing:
oxygen
glucose
and other essential substances.
If the heart suddenly stops pumping effectively because of an arrhythmia, cerebral blood flow can fall rapidly.
The person may:
become dizzy
lose consciousness
collapse
and sometimes develop convulsive movements.
If the underlying heart rhythm then returns to normal, the person may regain consciousness.
The event can therefore look neurological even though the original problem began in the heart.
What is an arrhythmia?
An arrhythmia is an abnormal heart rhythm.
The heart may beat:
too quickly
too slowly
or irregularly.
NHS guidance states that arrhythmias can cause:
palpitations
shortness of breath
light-headedness
dizziness
fainting
chest discomfort
or tiredness.
Some arrhythmias are relatively benign.
Others can be dangerous.
Why every first suspected seizure should include cardiac thinking
NICE's epilepsy guideline directs clinicians assessing a first suspected seizure to consider cardiac causes and the guidance on ECG assessment following transient loss of consciousness.
NICE's blackout quality standard says people who have had transient loss of consciousness should have a 12-lead ECG during their initial assessment.
The ECG is not looking for epilepsy.
It is looking for heart abnormalities that may provide an alternative explanation for the collapse.
What does an ECG do?
An electrocardiogram — ECG records the electrical activity of the heart.
Electrodes attached to the chest and limbs detect the timing and pattern of each heartbeat.
A standard ECG can reveal clues to problems such as:
abnormal conduction
slow heart rhythms
abnormal rhythms
prolonged or shortened QT intervals
Brugada-pattern abnormalities
ventricular pre-excitation
and evidence of other cardiac disease.
NICE specifies several ECG abnormalities that should be treated as warning signs after transient loss of consciousness.
What is long QT syndrome?
The heart's electrical system needs time to reset between beats.
The QT interval on an ECG represents part of that electrical recovery.
Some people have an abnormally prolonged QT interval.
This can increase the risk of dangerous ventricular arrhythmias.
Loss of consciousness caused by such an arrhythmia can sometimes be mistaken for an epileptic seizure.
This is one reason NICE includes long and short QT abnormalities among important ECG warning findings.
What is Brugada syndrome?
Brugada syndrome is a rare, often inherited heart-rhythm condition.
It can cause:
blackouts
dizziness
palpitations
seizure-like events
and potentially dangerous cardiac arrest.
NHS guidance specifically lists seizures or fits among possible presentations of Brugada syndrome because dangerous arrhythmia can reduce blood flow to the brain and cause collapse with seizure-like activity.
This does not mean Brugada syndrome is a common explanation for seizures.
It illustrates why heart assessment matters when the diagnosis is uncertain.
What is Wolff-Parkinson-White syndrome?
Some people are born with an additional electrical pathway in the heart.
This can allow episodes of abnormal rapid heart rhythm.
NICE specifically includes ventricular pre-excitation associated with Wolff-Parkinson-White syndrome among ECG findings clinicians should recognise when assessing blackouts.
Again, this is not a common explanation for every blackout.
The point is that particular cardiac disorders can sometimes masquerade as neurological events.
Cardiac red flags after a blackout
NICE recommends urgent cardiovascular assessment when transient loss of consciousness occurs alongside certain warning signs.
These include:
an abnormal ECG
known or suspected heart failure
loss of consciousness during exertion
family history of sudden cardiac death in someone younger than 40
known inherited cardiac disease
unexplained new breathlessness
or a heart murmur.
These features deserve attention even if the collapse looked like a seizure.
Fainting during exercise is particularly important
There is an important distinction between:
collapse during exercise
and:
fainting shortly after exercise stops.
NICE says syncope during exercise makes a cardiac arrhythmic cause more concerning.
Syncope occurring shortly after exercise is more commonly associated with a vasovagal mechanism.
A blackout during exertion therefore needs appropriate cardiac assessment.
Fainting while lying down can also be concerning
Ordinary vasovagal fainting is much more commonly associated with being upright.
The NHS advises calling 999 after a faint when the person fainted while lying down, as well as when there are other concerning features.
A collapse while lying down does not automatically mean heart disease, but it deserves careful assessment.
Family history matters
Doctors should ask whether relatives have had:
sudden unexplained death
inherited heart disease
serious arrhythmias
unexplained blackouts
or cardiac death at a young age.
NICE considers a family history of sudden cardiac death under age 40 or an inherited cardiac condition a red flag requiring urgent cardiovascular assessment.
This can be particularly important when an apparently healthy young person has unexplained collapse.
Palpitations matter too
A person might describe:
racing heartbeat
pounding
fluttering
skipped beats
or an irregular pulse
before a blackout.
NHS guidance on arrhythmias advises urgent assessment when palpitations occur with:
chest pain
breathlessness
dizziness
or fainting.
Palpitations do not automatically mean a dangerous arrhythmia.
But they should not be ignored in someone having unexplained loss of consciousness.
A normal ECG does not catch every intermittent arrhythmia
A standard ECG records the heart rhythm only during the short period when the test is performed.
If the abnormal rhythm occurs:
once a week
once a month
or only during a blackout,
the ordinary ECG may be normal between events.
When an arrhythmic cause is suspected, longer cardiac monitoring may be needed.
What is ambulatory ECG monitoring?
Ambulatory ECG monitoring records heart rhythm for longer than an ordinary ECG.
Depending on how frequently events happen, specialist testing can include:
an external event recorder
longer ambulatory monitoring
or an implantable event recorder.
NICE recommends choosing the monitoring method according to how often transient-loss-of-consciousness events occur.
For infrequent unexplained events, a very short Holter recording may simply miss the relevant rhythm.
What is an implantable loop recorder?
An implantable loop recorder, sometimes called an implantable event recorder, is a small device placed beneath the skin that continuously monitors heart rhythm over a much longer period.
It can be useful when:
blackouts are infrequent
an arrhythmia remains suspected
and short-term recordings have failed to capture an event.
NICE recommends implantable monitoring for some people with infrequent transient loss of consciousness when arrhythmia remains a concern.
What is postural hypotension?
Postural hypotension, also called orthostatic hypotension, is a fall in blood pressure after standing up.
It can cause:
dizziness
blurred vision
weakness
nausea
light-headedness
and fainting.
Possible contributing factors include:
dehydration
medicines
heart conditions
autonomic disorders
endocrine conditions
and other illnesses.
Why standing blood pressure may be checked
If postural hypotension is suspected, clinicians may compare blood pressure while:
lying down
and standing.
NICE recommends assessing lying and standing blood pressure when clinically appropriate during blackout assessment.
If the history strongly suggests postural hypotension but ordinary measurements do not confirm it, NICE recommends specialist cardiovascular assessment.
What is situational syncope?
Some faints occur reliably in particular circumstances.
Examples can include syncope triggered by:
coughing
swallowing
urinating
or straining.
NICE calls this situational syncope when there is a clear, consistent relationship and no alternative worrying features.
These events result from cardiovascular reflexes rather than epileptic activity.
What is a tilt-table test?
A tilt-table test examines how blood pressure and heart rate respond when a person is moved from lying towards a more upright position in a controlled setting.
It can sometimes help investigate recurrent reflex syncope.
But tilt testing is not needed for every ordinary faint.
NICE specifically says not to offer a tilt test when uncomplicated vasovagal syncope has already been confidently diagnosed during the initial assessment.
It may be considered in selected people with recurrent syncope, particularly when episodes significantly affect quality of life or create injury risk.
What if the person bites their tongue?
Tongue biting can provide useful information.
NICE recommends recording whether:
the tongue was bitten
and whether the injury involved the side or the tip.
Tongue injury can support the diagnosis of a convulsive epileptic seizure, particularly when other seizure features are present.
But it should still be interpreted as part of the whole event rather than being treated as a perfect test.
What about urinary incontinence?
Urinary incontinence can occur during epileptic seizures.
However, it is not sufficiently specific to diagnose epilepsy by itself.
Loss of bladder control can occur with other forms of transient loss of consciousness.
A clinician should therefore not decide:
“There was incontinence, so this must have been epilepsy.”
The sequence and other features still matter.
What about the eyes?
Witnesses are often asked:
were the eyes open?
were they closed?
did they deviate to one side?
NICE includes eye appearance among the details that should be recorded after transient loss of consciousness.
Eye position can sometimes contribute useful information, but it is not diagnostic on its own.
What about head turning?
Sustained head turning to one side during loss of consciousness is one of the features NICE identifies as strongly suggestive of an epileptic seizure.
It can be particularly useful if it repeatedly occurs at the beginning of similar events.
But a witness should describe exactly what they saw rather than attempting to decide which side of the brain was involved.
Duration matters — but witnesses often estimate it badly
A collapse can feel dramatically longer than it really was.
If safe, use a clock or phone to time:
loss of consciousness
abnormal movements
and recovery.
NICE recommends recording the duration from onset through return of consciousness.
Try to distinguish:
active movement
from:
subsequent confusion or tiredness.
Why witness accounts are so important
The person who lost consciousness may remember:
nothing
only the warning
or only waking afterwards.
NICE therefore recommends obtaining accounts from witnesses whenever possible.
A useful witness description includes:
posture before collapse
warning symptoms
skin colour
eye position
movement
duration
tongue biting
injuries
and recovery.
Video can help
When the diagnosis remains unclear, NICE advises people with recurrent transient loss of consciousness to try to record future events through:
video
or detailed witness accounts.
A good recording may help distinguish:
epileptic seizures
convulsive syncope
functional attacks
and some movement phenomena.
Safety always takes priority over filming.
Related Information Hub page:
Seizure Diaries and Videos: How to Record Useful Evidence
Why an EEG is not the first test for every blackout
An EEG records brain electrical activity.
It can be useful when the history suggests epilepsy.
But NICE specifically says not to routinely use EEG in the investigation of transient loss of consciousness itself.
Why?
Because the first question is whether the event was:
epileptic
cardiovascular
fainting
or another type of blackout.
A routine EEG cannot safely replace that broader assessment.
A normal EEG does not turn the event into a faint
Just as importantly:
normal EEG ≠ syncope.
A person with genuine epilepsy may have a normal routine EEG.
The diagnosis still depends on:
history
witnesses
ECG
neurological assessment
EEG where appropriate
and sometimes prolonged monitoring.
Related Information Hub page:
EEG: What It Can — and Cannot — Tell You About Epilepsy
What if the person already has epilepsy?
An established epilepsy diagnosis should not automatically explain every future collapse.
Someone with epilepsy can also develop:
vasovagal syncope
postural hypotension
heart disease
medication-related low blood pressure
functional seizures
or another condition.
A new event that looks different from the person's normal seizures deserves assessment rather than being automatically labelled:
“another seizure.”
What if the person already has a heart condition?
The same principle works in reverse.
Someone with known:
arrhythmia
vasovagal syncope
or postural hypotension
can still develop epilepsy.
An existing cardiac diagnosis should not automatically explain a new event with strongly epileptic features.
More than one condition can coexist.
Can epilepsy itself affect heart rhythm?
Yes, occasionally.
Some epileptic seizures can produce significant changes in:
heart rate
cardiac rhythm
or autonomic function.
Rarely, focal seizures can be associated with marked slowing of the heart or ictal asystole.
NICE specifically reminds clinicians that more than one mechanism may coexist and gives ictal arrhythmias as an example when blackouts remain unexplained.
This is a separate specialist subject and deserves its own Information Hub page.
Planned related page:
Ictal Asystole and Seizure-Related Bradycardia
Does an abnormal heart rate during a seizure prove the heart caused it?
No.
Heart-rate changes commonly occur because of seizure-related autonomic activity.
So the important question may be:
Did the abnormal heart rhythm cause the loss of consciousness?
or:
Did the seizure cause the heart-rate change?
Simultaneous EEG and ECG monitoring can sometimes help establish the sequence.
What if both EEG and ECG need recording?
Video EEG telemetry normally includes ECG monitoring alongside EEG in many specialist units.
For particularly difficult cases, clinicians may need to compare:
seizure behaviour
brain electrical activity
and heart rhythm
during the same event.
This can be extremely useful when neurological and cardiovascular explanations overlap.
Functional events can also resemble blackouts
Functional seizures or functional episodes can also cause:
apparent unconsciousness
falls
shaking
or prolonged unresponsiveness.
NICE advises considering functional non-epileptic seizures or psychogenic pseudosyncope when transient loss of consciousness remains persistent and unexplained, particularly when event characteristics change or episodes are unusually prolonged.
These are genuine involuntary conditions and require appropriate specialist assessment.
This subject is covered separately so that it is not reduced to a brief “diagnosis of exclusion”.
Related Information Hub page:
Second Opinions and Re-evaluating an Epilepsy Diagnosis
Blood sugar can also cause collapse and seizure-like events
Severe hypoglycaemia can cause:
sweating
confusion
abnormal behaviour
loss of consciousness
and seizures.
NICE recommends relevant blood testing when the history suggests an underlying metabolic cause.
This is why not every episode belongs solely to either:
heart
or:
epilepsy.
The wider medical picture matters.
Related Information Hub page:
Blood Tests, Lumbar Puncture and Antibody Testing in Epilepsy
Medicines can contribute to blackouts
Medication may contribute to:
low blood pressure
abnormal heart rhythm
dehydration
sedation
or interactions.
NICE therefore recommends reviewing current medication during assessment of transient loss of consciousness.
This includes medicines prescribed for conditions other than epilepsy.
When should 999 be called after a faint or blackout?
NHS guidance says emergency help is appropriate when someone who has fainted:
is not breathing
cannot be woken within 1 minute
has not fully recovered
has difficulty speaking or moving
has chest pain
has a pounding, fluttering or irregular heartbeat
has serious injury
is shaking or jerking
fainted while exercising
or fainted while lying down.
If someone is not breathing normally or is unresponsive with signs of cardiac arrest, follow emergency operator instructions immediately.
What if the person wakes quickly and feels fine?
A classic uncomplicated faint may resolve rapidly.
But a first unexplained blackout still deserves appropriate medical assessment.
The urgency depends on:
circumstances
age
medical history
ECG
injury
and whether any red flags were present.
A quick recovery is useful diagnostic information.
It is not an automatic guarantee that the event was harmless.
Questions a clinician may ask
After a blackout, useful questions include:
What were you doing immediately beforehand?
Were you standing, sitting or lying down?
Had you been standing for a long time?
Did you feel hot, sweaty or nauseated?
Did your vision fade?
Did you feel your heart racing?
Did you have chest pain?
Did you experience déjà vu or another unusual focal sensation?
What did witnesses see first?
Did your head turn?
Did your body stiffen?
How long did any jerking last?
Did you bite your tongue?
What colour were you?
How quickly did you recover?
Were you confused afterwards?
Has this happened before?
Has anyone in your family died suddenly at a young age?
The answers can substantially alter which investigation comes next.
What information should a witness record?
Useful witness notes include:
Before
standing, sitting, lying or exercising
complaints of dizziness or nausea
sweating
palpitations
unusual behaviour
aura-like symptoms
During
colour
eyes
head position
body stiffening
limb movements
responsiveness
breathing
duration
After
immediate recovery
confusion
weakness
speech problems
sleepiness
injury
A factual observation is more useful than a conclusion.
Write:
“became very pale and had four or five brief jerks”
rather than:
“had an epileptic seizure.”
Questions to ask after an unexplained blackout
Useful questions include:
Could this have been syncope rather than epilepsy?
Was my ECG normal?
Was the QT interval normal?
Do I have any cardiac red flags?
Do I need longer heart-rhythm monitoring?
Could postural hypotension explain this?
Should lying and standing blood pressure be checked?
Was the jerking brief enough to occur during syncope?
Which features make you think this was epileptic?
Do I need an epilepsy assessment?
Do I need a cardiology assessment?
Would video EEG help?
Could both heart rhythm and EEG be monitored during an event?
If epilepsy and cardiology specialists disagree
Sometimes one specialist suspects:
epilepsy
while another suspects:
syncope or arrhythmia.
The safest response is not necessarily to choose one specialty.
It may be necessary to gather better evidence.
That can include:
video
witness accounts
repeat ECG review
prolonged cardiac monitoring
video EEG
blood-pressure testing
or investigation of more than one possible mechanism.
NICE specifically advises considering multiple coexisting causes when transient loss of consciousness remains unexplained.
The most important message
Collapse plus jerking does not automatically equal epilepsy.
A temporary reduction of blood flow to the brain during syncope can sometimes produce:
stiffening
twitching
or seizure-like movements.
This is why clinicians need to understand:
what happened before, during and after the event.
Features such as:
prolonged standing
feeling hot
sweating
nausea
pallor
and improvement on lying down
may support syncope.
Features such as:
sustained head turning
unusual posturing
prolonged jerking
tongue biting
post-event confusion
and déjà vu or jamais vu
may make epilepsy more likely.
But no single feature is perfect.
Heart problems also matter.
Potentially serious arrhythmias can cause sudden loss of consciousness and may occasionally produce seizure-like activity.
That is why ECG assessment is an important part of evaluating unexplained blackouts.
And the distinction is not always:
heart or brain.
A person can have epilepsy and syncope.
They can have epilepsy and heart disease.
Rarely, an epileptic seizure itself can disturb cardiac rhythm.
The correct diagnosis comes from reconstructing the whole event and choosing investigations that test the competing explanations rather than assuming that every collapse with movement must have started in the brain.
Sources and further reading
NICE — Transient loss of consciousness ('blackouts') in over 16s, CG109.
Current NICE guidance provides the core UK framework for distinguishing uncomplicated faint, cardiovascular syncope and suspected epileptic seizures. It specifically notes that brief seizure-like movements can occur during uncomplicated syncope and identifies features supporting epilepsy and cardiovascular red flags.
NICE Quality Standard QS71 — Initial assessment after transient loss of consciousness.
NICE recommends a detailed account of the event, witness history, examination and 12-lead ECG.
NICE — Epilepsies in children, young people and adults, NG217.
Current epilepsy guidance requires clinicians assessing a first suspected seizure to take a detailed history and consider the NICE transient-loss-of-consciousness pathway, including ECG and possible cardiac causes.
NHS — Fainting.
Current NHS information covering fainting symptoms, emergency warning signs and when urgent help is needed.
NHS — Heart rhythm problems (arrhythmia).
Current NHS guidance describes arrhythmias and symptoms including palpitations, dizziness and fainting, with emergency advice when significant cardiovascular symptoms occur together.
NHS — Brugada syndrome.
Current guidance on this inherited cardiac rhythm disorder, including blackouts, palpitations and seizure-like events as possible presentations.
Guy's and St Thomas' NHS Foundation Trust — Postural hypotension.
Current NHS information explaining the drop in blood pressure on standing and associated dizziness, weakness and fainting. Reviewed September 2025.
Royal Brompton and Harefield Hospitals — Vasovagal syncope.
NHS specialist information on common fainting, warning symptoms, blood-pressure changes and common provoking factors.
Information reviewed: September 2026.
This page provides general educational information. A first unexplained blackout, a blackout with cardiac warning signs, or an event significantly different from a person's established seizures should receive appropriate medical assessment.
