How to Prevent Vasovagal Syncope

Vasovagal syncope is a condition that can lead to fainting. The onset of vasovagal syncope attack symptoms may be rapid and give little time to act - however, using certain tried and tested tricks can help to prevent fainting once you recognise the signs. 

To prevent fainting, it is important to maintain blood flow to the brain - the simplest and most effective way to do this is to lie down and elevate your legs.1 If it is impractical to lie down, you may also sit down and place your head between your knees.1 Tensing the arm or leg muscles can also help you to remain conscious.2

Understanding the causes of vasovagal syncope can help you to care for yourself or others who may be experiencing a fainting spell. Read on to find out how to prevent fainting, and what to do following an unexpected loss of consciousness. 

What is vasovagal syncope?

Vasovagal syncope is a condition that may occur when your body overreacts to certain triggers, which causes you to faint (pass out).1 Common triggers that may cause a vasovagal syncope episode include extreme emotional distress, standing up for a long time, or seeing blood and medical instruments.2 

According to the American Heart Association, vasovagal syncope is more common in children and young adults, but it can occur at any age.3 

Other terms for a vasovagal syncope include: neurally mediated syncope (NMS), reflex syncope, neurocardiogenic syncope, and vasodepressor syncope.3

Symptoms of vasovagal syncope

In the 30-60 seconds before fainting, people with vasovagal syncope may experience the following symptoms:2

  • Lightheadedness or dizziness
  • Pale skin
  • Visual disturbances (e.g. blurred vision, or tunnel vision)
  • Nausea (feeling that you might be sick)
  • Feeling warm
  • Cold or clammy sweat
  • Sudden tiredness
  • Yawning

Once the vasovagal syncope attack starts, the person loses consciousness, which usually lasts for no more than 15 seconds.2 They will also fall to the ground unless supported.2 The fall can sometimes cause an injury, depending on the safety of the surroundings. 

Bystanders may observe the following signs in the person experiencing a vasovagal syncope attack:

  • Eyes roll up and back into the head (remaining open)1
  • Jerky, twitchy, or abnormal movements1
  • Dilated (enlarged) pupils1
  • Slow, weak pulse1
  • Loss of control of the bladder2
  • No interruption in breathing2

After regaining consciousness, the person who has fainted will generally start to feel better in less than a minute.1 He or she may experience some transient symptoms before their full recovery, such as:2

  • Anxiety
  • Confusion
  • Tiredness
  • Dizziness
  • Urge to use the bathroom
  • Sweating
  • Pale skin
  • Headache

If the person stands up too soon after fainting (within 15-30 minutes), they may be at risk of fainting again.1

What causes vasovagal syncope?

Vasovagal syncope is a natural reflex reaction that happens in the body - however, when the reaction is too strong, or happens at the wrong time, the person may faint.2 

The vagus nerve is a part of the nervous system that regulates heart rate and blood pressure.2 It may malfunction (become too active) in response to a trigger, such as the sight of blood, or extreme emotional distress - the malfunction can cause blood pressure to drop rapidly, as blood vessels widen and blood accumulates in the legs.2 If the drop in heart rate and blood pressure is too strong or too fast, blood flow to the brain may be inadequate, which can cause an attack of vasovagal syncope (fainting).2

What can trigger vasovagal syncope?

Certain common triggers are often responsible for vasovagal syncope episodes. These include:1

  • Standing up for a long time
  • Heat exposure
  • Seeing blood
  • Having blood drawn 
  • Seeing medical instruments
  • Fear of injury to the body
  • Severe emotional distress
  • Straining (e.g. trying to have a bowel movement)

It is important to understand what triggers your vasovagal syncope in order to avoid the triggers in the future. 

How is vasovagal syncope diagnosed and treated?

Vasovagal syncope is usually harmless, and most people who experience it will require little or no treatment.1 However, diagnostic tests may be necessary to ascertain that no serious condition, such as a heart disorder, has caused the fainting spell.4 

Diagnosis of vasovagal syncope

The diagnosis of vasovagal syncope usually begins with a physical examination; the doctor may measure the blood pressure and heart rate.1

The doctor may then ask some questions to better understand the circumstances in which you fainted, as well as some of your relevant medical information, such as:1

  • What were you doing just before you fainted?
  • Did you experience any symptoms before you fainted?
  • Have you ever fainted before?
  • Are you taking any medication?
  • Have you ever had a head injury?
  • Has anyone in your family died suddenly of a heart attack or heart failure?

After an initial physical examination, the doctor may perform some further tests to rule out other possible causes of fainting. 

The tilt test is commonly used to determine a patient’s susceptibility to vasovagal syncope (or reflex fainting).3 During the tilt test, the patient is asked to lie down on a board, and the heart rate and blood pressure are measured. The board is then tilted up - people with vasovagal syncope will usually faint during the tilting, as the motion causes their blood pressure and heart rate to drop rapidly.3 When the patient returns to a horizontal position, blood flow to the brain is restored, and he or she regains consciousness.3

Diagnostic tests for the heart may also be carried out to rule out any underlying conditions that may have caused the fainting spell. This can include an electrocardiogram, in which the electrical activity of the heart is measured.1 

Treatment of vasovagal syncope

Vasovagal syncope is usually harmless, and treatment is normally unnecessary.1 Talking to your doctor can help you to identify triggers that may cause you to faint, so that you can take care to avoid them in the future. 

If frequent fainting is affecting the patient’s quality of life, the doctor may recommend medication, such as fludrocortisone acetate (a drug that is normally used to treat low blood pressure).1 It may also be recommended to increase salt in the diet.1

The doctor may recommend foot exercises or using compression stockings,1 or simply tensing the leg muscles when standing for a long time.2 

In very rare cases, where other treatments for vasovagal syncope are ineffective, the patient may receive a pacemaker to regulate their heart rate.5 A pacemaker6 is a device that is surgically inserted under the skin near the left clavicle - it regulates the heart rhythm, which may help to prevent sudden drops in heart rate, thus avoiding vasovagal syncope.5 

Does vasovagal syncope ever go away?

One in three people will experience vasovagal syncope at least once in their life.2 For some, this can be an isolated episode, but for others, the condition can result in recurrent syncope episodes. 

How do you prevent vasovagal syncope?

If you are starting to feel the early signs of a vasovagal syncope episode, try one of the following physical manoeuvres to keep blood higher in the body and prevent fainting: 

  • Lie down and lift your legs (above the level of the heart)1
  • If you cannot lie down, sit down and put your head between your knees1
  • Squeeze a foam or rubber ball - clenching the fists may help you stay conscious2
  • Tense your arm muscles2
  • Tense your leg muscles while standing: cross your legs, placing one knee behind the other, and tense your muscles in the legs, belly, and buttocks2

What are the treatment options?

Vasovagal syncope is usually harmless, and most people who experience it need little or no treatment.1

Some treatment may be required due to the circumstances in which the patient has fainted. A sudden fainting spell can cause an injury, for example, if the patient falls in an unsafe position and hits their head - once they come to, treatment may be required for these physical injuries on a case-by-case basis.1

If the person who has fainted is dehydrated, they may need to receive fluids through an IV (administering fluids directly into a person’s vein).2

In rare cases, further diagnostic tests may determine that a serious condition may have caused the fainting spell - medication and treatment will likely be needed in these cases, which is why it is crucial that you see a doctor if you have fainted unexpectedly.2

When to see a doctor 

If you have fainted for the first time, it is important to see a doctor - besides vasovagal syncope, fainting can sometimes indicate a more serious condition (such as a heart or brain disorder). The doctor may perform some diagnostic tests to determine if any underlying conditions have caused the fainting spell.1 

It is also important to see a doctor if you have never fainted before, but you have had several instances where you felt like you were going to pass out.2

Seek medical attention immediately if you have hit your head after fainting and falling,2 as this can result in an injury, such as a concussion.7

If you have previously been diagnosed with vasovagal syncope, but the symptoms of your vasovagal syncope spells change, or the fainting becomes more frequent, see a doctor, as further tests may be needed.2


Restoring adequate blood flow to the brain is key to preventing vasovagal syncope (fainting); this can be achieved by laying down with legs lifted, sitting down with your head between your knees, or muscle tensing. 


  1. Mayo Clinic. Vasovagal syncope. [Internet]. [Cited 25 December 2022]. Available from:
  2. Cleveland Clinic. Vasovagal Syncope. [Internet] [Cited 25 December 2022]. Available from:
  3. American Heart Association. Syncope (Fainting). [Internet] [Cited 25 December 2022]. Available from:
  4. Sheldon R, Rose S, Connolly S, Ritchie D, Koshman M, Frenneaux. Diagnostic criteria for vasovagal syncope based on a quantitative history. Eur Jeart J. 2005 Oct 13;27: 344-350
  5. Gopinathannair R, Salgado BC, Olshansky B. Pacing for vasovagal syncope. Arrhythm Electrophysiol Rev. 2018 Jun;7(2):95-102
  6. NHS. Pacemaker implantation. [Internet]. [Cited 30 December 2022]. Available from:
  7. NHS Inform. Concussion. [Internet]. [Cited 30 December 2022]. Available from:
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Katarzyna Drzewinska

Master of Biology, Bachelor of Science, Biochemistry, University of Leeds

Katarzyna is a graduate of the MBiol, BSc Biochemistry (International) programme from the University of Leeds, UK. Her previous laboratory research projects have focussed on environmental microplastics and natural product discovery (antibiotics), but she has found her true passion in medical writing - particularly making scientific literature accessible for the general reader.

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