---
title: Vasovagal syncope
description: What reflex (vasovagal) syncope is, why pain, fear or standing for a long time can make you faint, how it differs from fainting caused by heart disease, how it is recognised and prevented, and when to call an ambulance.
type: disease
aliases:
  - reflex syncope
  - neurally mediated syncope
  - neurocardiogenic syncope
  - situational syncope
  - uncomplicated faint
  - fainting
  - faint
  - syncope
  - VVS
sources:
  - tier: guideline
    org: esc
    title: Рекомендации ЕОК по диагностике и лечению синкопальных состояний 2018
    year: 2019
    doi: 10.15829/1560-4071-2019-7-130-194
    url: https://doi.org/10.15829/1560-4071-2019-7-130-194
  - tier: guideline
    org: nice
    title: Transient loss of consciousness ('blackouts') in over 16s (CG109)
    year: 2023
    url: https://www.nice.org.uk/guidance/cg109
  - tier: reference
    org: msd-manuals
    title: Syncope
    year: 2024
    url: https://www.msdmanuals.com/professional/cardiovascular-disorders/symptoms-of-cardiovascular-disorders/syncope
  - tier: reference
    org: msd-manuals
    title: Fainting (Consumer Version)
    year: 2024
    url: https://www.msdmanuals.com/home/heart-and-blood-vessel-disorders/symptoms-of-heart-and-blood-vessel-disorders/fainting
  - tier: reference
    org: statpearls
    title: Vasovagal Episode
    year: 2023
    url: https://www.ncbi.nlm.nih.gov/books/NBK470277/
sources_checked: 2026-10-13
review: null
---

Syncope is a brief loss of consciousness because, for a short time, the brain gets too little blood. It starts suddenly, does not last long and goes away by itself, with complete recovery.<Cite n={[1, 2]} /> Syncope is called reflex syncope when blood pressure falls and/or the heart rate slows as a reflex response to something, such as pain, prolonged standing or emotional stress.<Cite n={2} /> Vasovagal syncope is the most common form of reflex syncope.<Cite n={5} /> In itself it is not dangerous unless the person is injured when they fall.<Cite n={4} /> But fainting caused by heart disease can look the same, so anyone who has fainted should see a doctor: only a doctor can tell a harmless cause from a serious one.<Cite n={4} />

<Diagram name="vasovagal-syncope">
  <p slot="normal">
    The person is standing. To keep blood pressure up, the body quickly adjusts the heart rate and
    the tone of the blood vessels, and active leg muscles help return blood to the heart.<Cite
      n={4}
    /> While blood pressure holds, the brain gets enough blood.<Cite n={[1, 4]} />
  </p>
  <p slot="disease">
    A trigger, such as pain, fear or prolonged standing, sets off a reflex.<Cite n={[1, 2]} /> Strong
    emotion or pain activates the vagus nerve: blood vessels widen, less blood returns to the heart
    and the heart rate slows.<Cite n={4} /> Blood pressure falls and, for a short time, the brain
    gets too little blood: light-headedness follows, and sometimes fainting.<Cite n={[1, 4]} />
    Which response occurs, a fall in blood pressure, a slower heart rate or both, does not depend
    on the trigger.<Cite n={1} />
  </p>
</Diagram>

## Why it happens

<Patient>

Vasovagal syncope is often, but not always, triggered by pain, prolonged standing (especially in a warm place) or emotional stress.<Cite n={2} /> Other triggers are fear, medical procedures and the sight of blood.<Cite n={[1, 4]} /> Even a healthy person may faint after standing still for a long time, because the leg muscles have to be active to help return blood to the heart.<Cite n={4} />

Situational syncope, which happens when passing urine, coughing, sneezing or swallowing, is also a form of reflex syncope.<Cite n={[1, 2]} /> Fainting is more likely when several factors come together: medicines that lower blood pressure, alcohol, drinking too little, losing fluid through vomiting or diarrhoea, and heat.<Cite n={1} />

</Patient>

<Student>

The ESC distinguishes two main mechanisms of reflex syncope. In the vasodepressor type, hypotension results from insufficient sympathetically mediated vasoconstriction. In the cardioinhibitory type, bradycardia or asystole predominates, reflecting a shift of autonomic balance towards parasympathetic tone.<Cite n={1} /> The StatPearls review describes the mechanism as complex, involving both decreased cardiac output and decreased vascular tone.<Cite n={5} /> The haemodynamic response (cardioinhibitory, vasodepressor or both) is independent of the trigger.<Cite n={1} />

The final common pathway of all syncope is a fall in systemic blood pressure with a decrease in global cerebral blood flow; sudden cessation of cerebral blood flow for 6–8 seconds can cause complete loss of consciousness.<Cite n={1} /> In NICE terminology, a 'faint' is an episode of transient loss of consciousness due to vasovagal syncope.<Cite n={2} />

</Student>

## Symptoms

<Patient>

Fainting is usually preceded by warning symptoms that build up gradually: pallor, sweating, nausea, feeling warm, weakness, yawning and blurred vision.<Cite n={[1, 2, 3]} /> Some people notice tunnel vision or tingling of the lips or fingertips.<Cite n={4} />

During a faint the person is motionless and limp, with cool hands and feet, a weak pulse and shallow breathing. Sometimes there are brief muscle jerks that look like a seizure.<Cite n={3} /> This does not necessarily mean epilepsy.<Cite n={2} />

When the person falls down or lies down, blood flow to the brain increases and consciousness quickly returns. But they may not feel completely normal for a few minutes to a few hours, and some feel very tired.<Cite n={4} />

</Patient>

<Student>

NICE advises diagnosing an uncomplicated faint on the basis of the initial assessment when there are no features suggesting an alternative diagnosis and there are features of the 3 'P's: posture (prolonged standing, or similar episodes that have been prevented by lying down), provoking factors (such as pain or a medical procedure) and prodromal symptoms (such as sweating or feeling warm/hot).<Cite n={2} /> According to the ESC, vasovagal syncope is highly probable if it is precipitated by pain, fear or standing and is associated with a typical progressive prodrome.<Cite n={1} />

The ESC lists as features of reflex syncope a long history of recurrent syncope, particularly before the age of 40, an association with crowded places or heat, and the absence of cardiovascular disease.<Cite n={1} /> Jerking or convulsions lasting more than a few seconds, incontinence, drooling and tongue biting usually point to a seizure rather than syncope.<Cite n={[2, 3]} />

</Student>

## How it is diagnosed

<Patient>

The most important part is a detailed account: what the person was doing, whether they were standing or lying down and for how long, and what they felt before fainting.<Cite n={4} /> A description from witnesses matters, because the person who fainted may not remember what happened.<Cite n={[1, 4]} /> The doctor examines the person, measures blood pressure lying down and standing, and records an [ECG](../../diagnostic/ecg/).<Cite n={[2, 4]} /> If the picture is typical, no further tests are needed.<Cite n={1} />

If the diagnosis is unclear, a tilt test is sometimes done: the person lies on a table that is tilted head-up while heart rate and blood pressure are measured continuously, to see whether a tendency to vasovagal syncope can be provoked.<Cite n={[1, 2]} /> If the doctor suspects a heart rhythm disorder, the rhythm is recorded first: see the article on [Holter monitoring](../../diagnostic/holter-monitoring/).<Cite n={2} />

</Patient>

<Student>

NICE advises against a tilt test for people who have a diagnosis of vasovagal syncope on initial assessment. For recurrent episodes that adversely affect quality of life or carry a high risk of injury, a tilt test is considered only to assess whether there is a severe cardioinhibitory response (usually asystole).<Cite n={2} /> The ESC recommends that a tilt test be considered in suspected reflex syncope. Syncope induced during tilt testing corresponds clinically to syncope triggered by prolonged standing, but a negative test does not exclude reflex syncope, and the test reveals a susceptibility to hypotension rather than establishing a diagnosis.<Cite n={1} /> For a suspected arrhythmic cause, NICE recommends ambulatory ECG rather than a tilt test as the first-line investigation.<Cite n={2} />

Features pointing to cardiac syncope are syncope during exertion or when lying down, sudden palpitations followed by syncope, a family history of unexplained sudden death at a young age, and structural heart disease or coronary artery disease.<Cite n={1} /> Syncope that begins and ends suddenly is typical of cardiac causes, most commonly an arrhythmia; syncope while lying down also suggests an arrhythmia, because the vasovagal mechanism does not cause syncope in the recumbent position.<Cite n={3} /> NICE advises distinguishing syncope during exercise (a cardiac arrhythmic cause is probable) from syncope shortly after stopping exercise (a vasovagal cause is more likely).<Cite n={2} /> Cardiac causes are covered in the articles on [AV block](../av-block/), [sick sinus syndrome](../sick-sinus-syndrome/), [ventricular tachycardia](../ventricular-tachycardia/), [aortic stenosis](../aortic-stenosis/) and [hypertrophic cardiomyopathy](../hypertrophic-cardiomyopathy/).<Cite n={1} />

</Student>

## How it is treated

<Patient>

Treatment is based on non-drug measures: explanation, education and changes in habits.<Cite n={1} /> The doctor explains why the faints happen, reassures the person that the outlook is good, and helps them recognise and avoid their triggers.<Cite n={2} /> If the triggers are unclear, it helps to keep a record of when episodes happen and what the person was doing at the time.<Cite n={2} />

At the first warning symptoms, sit or lie down straight away.<Cite n={1} /> A doctor may advise drinking more fluids.<Cite n={1} /> If the warning symptoms last long enough, physical counter-pressure manoeuvres help: tensing the muscles of the legs or arms raises blood pressure and in most cases helps to avoid or delay loss of consciousness. They work best in people younger than 60.<Cite n={1} /> A doctor will show how to do them.

If the person takes medicines that lower blood pressure, the doctor may review them.<Cite n={1} /> Do not change or stop these medicines yourself: see the article on [high blood pressure](../hypertension/). Medicines for fainting or a pacemaker are rarely needed, and the doctor decides on them.<Cite n={1} /> Do not drive until a doctor has found the cause of the loss of consciousness.<Cite n={[2, 4]} />

</Patient>

<Student>

The ESC recommends for all patients an explanation of the diagnosis, reassurance, and explanation of the risk of recurrence and of how to avoid triggers and situations. By consensus, education and lifestyle modification are first-line therapy in all cases.<Cite n={1} /> According to data cited by the ESC, more than half of the patients with recurrent syncope in the 1–2 years before evaluation have no further episodes in the following 1–2 years; the authors consider the effect of education and reassurance the most likely main reason.<Cite n={1} />

Isometric physical counter-pressure manoeuvres are a class IIa (B) option in patients younger than 60 with a prodrome. Modification or withdrawal of hypotensive drugs should be considered in vasodepressor syncope (IIa, B).<Cite n={1} /> Drug therapy may be considered when syncope keeps recurring despite education, lifestyle modification and training in counter-pressure manoeuvres. Cardiac pacing is a last resort and only for patients selected by strict criteria: for example, aged 40 or over (more often over 60) with severe forms of reflex syncope and frequent recurrences carrying a high risk of injury, often because of the absence of a prodrome.<Cite n={1} /> No treatment can completely prevent recurrences.<Cite n={1} />

</Student>

## When to call an ambulance

**If the faint looks typical.** Check whether the person is breathing. If they are, let them stay lying down: sitting up too quickly can bring the faint back.<Cite n={4} /> While the person lies down, blood flow to the brain increases and consciousness quickly returns.<Cite n={4} /> Even if everything has passed, see a doctor after fainting.<Cite n={4} />

**Call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK)** if there are signs that may point to a heart cause or a dangerous condition:<Cite n={[1, 2, 4]} />

- the person does not fully regain consciousness;<Cite n={2} />
- the person is not breathing: call and start cardiopulmonary resuscitation (CPR), and use an automated external defibrillator (AED) if one is available;<Cite n={4} />
- the faint happened during physical exertion or while lying down;<Cite n={[1, 2]} />
- sudden palpitations came just before the faint;<Cite n={1} />
- new chest pain or discomfort, breathlessness, abdominal pain or headache came before or after the faint;<Cite n={[1, 4]} />
- the person was seriously injured in the fall.<Cite n={4} />

**See a doctor without delay** if the faint came suddenly, without warning symptoms or an obvious trigger, if faints recur within a short time, if there is heart failure or other heart disease or an abnormal ECG, or if a family member died suddenly of a heart cause before the age of 40 or there is an inherited heart condition.<Cite n={[1, 2, 4]} /> NICE also suggests considering an equally urgent cardiovascular assessment, within 24 hours, for anyone older than 65 who has fainted without warning symptoms.<Cite n={2} />

<Quiz />