When you faint, you'll feel weak and unsteady before passing out for a short period of time, usually only a few seconds.
There may not be any warning symptoms, but some people experience:
Read more about the symptoms of fainting .
If you feel you're about to faint, lie down, preferably in a position where your head is low and your legs are raised. This will encourage blood flow to your brain.
If it's not possible to lie down, sit with your head between your knees. If you think someone is about to faint, you should help them lie down or sit with their head between their knees.
If a person faints and doesn't regain consciousness within one or two minutes, put them into the recovery position .
You should call emergency services, ask for an ambulance and stay with the person until medical help arrives.
Most cases of fainting aren't a cause for concern and don't require treatment, but less common types of fainting can be medical emergencies.
You should see your doctor after fainting if you:
If your first episode of fainting occurs after 40, it may be a sign of a more serious underlying problem.
Read more about diagnosing fainting .
The brain relies on oxygen carried in the blood to function properly. Fainting can occur when the blood flow to the brain is reduced.
Your body usually corrects reduced blood flow to the brain quickly, but it can make you feel odd, sweaty and dizzy. If it lasts long enough, you may faint.
Reduced blood flow to the brain is often caused by a temporary problem with the part of your nervous system that regulates the body's automatic functions, including heartbeat and blood pressure.
This type of fainting is called neurally mediated syncope. It can be triggered by:
Read more about the causes of fainting .
Treatment for fainting will depend on the type you're experiencing. In many cases of neurally mediated syncope, no further treatment is needed.
If you've had a fainting episode, you can avoid it happening again by:
Read more about how fainting is treated .
Fainting can occur when you're sitting, standing, or when you get up too quickly.
You may not experience any warning symptoms before losing consciousness and, if you do, it may only be for a few seconds.
You may experience the following symptoms just before fainting:
This will usually be followed by a loss of strength and consciousness.
When you collapse to the ground, your head and heart are on the same level. This means your heart doesn't have to work as hard to push blood up to your brain.
You should return to consciousness after about 20 seconds.
Call emergency services and ask for an ambulance if someone faints and doesn't regain consciousness within two minutes.
After fainting, you may feel confused and weak for about 20-30 minutes. You may also feel tired and not be able to remember what you were doing just before you fainted.
Fainting can sometimes be mistaken for a serious medical condition, such as a stroke . A stroke is a medical emergency that occurs when blood supply to the brain is interrupted.
You should call emergency services immediately and ask for an ambulance if you think you or someone else is having a stroke.
The main symptoms of stroke can be remembered with the word FAST, which stands for Face-Arms-Speech-Time:
Read more about symptoms of a stroke .
Blood flow to the brain can be interrupted for a number of reasons. The different causes of fainting are explained below.
Fainting is most commonly caused by a temporary glitch in the autonomic nervous system. This is sometimes known as neurally mediated syncope.
The autonomic nervous system is made up of the brain, nerves and spinal cord. It regulates automatic bodily functions, such as heart rate and blood pressure.
An external trigger can temporarily cause the autonomic nervous system to stop working properly, resulting in a fall in blood pressure and fainting.
The trigger may also cause your heartbeat to slow down or pause for a few seconds, resulting in a temporary interruption to the brain's blood supply. This is called vasovagal syncope.
The trigger may be:
Fainting can also be caused by a fall in blood pressure when you stand up. This is called orthostatic hypotension , and tends to affect older people, particularly those aged over 65. It's a common cause of falls in older people.
When you stand up after sitting or lying down, gravity pulls blood down into your legs, which reduces your blood pressure.
The nervous system usually counteracts this by making your heart beat faster and narrowing your blood vessels. This stabilises your blood pressure.
However, in cases of orthostatic hypotension, this doesn't happen, leading to the brain's blood supply being interrupted and causing you to faint.
Possible triggers of orthostatic hypotension include:
Heart problems can also interrupt the brain's blood supply and cause fainting. This type of fainting is called cardiac syncope.
The risk of developing cardiac syncope increases with age. You're also at increased risk if you have:
See your doctor as soon as possible if you think your fainting is related to a heart problem.
A reflex anoxic seizure (RAS) is a type of fainting that mainly occurs in young children. It's caused by an involuntary slowing of the heart rate, to the extent that the heart actually stops beating for 5-30 seconds.
The child will often open their mouth as if they're going to cry, but make no sound before turning pale grey and losing consciousness.
They'll either become limp – or, more often, stiff – with their eyes rolling upwards and their fingers clawed. Their body may also jerk a few times.
The seizure usually lasts less than a minute. Afterwards, the child will regain consciousness, but may appear sleepy and confused for a few hours.
Reflex anoxic seizures can be frightening to witness, but they aren't dangerous and don't harm the child.
The seizures will become less frequent as the child gets older and usually disappear by the time they're four or five years of age.
Read more about reflex anoxic seizures .
Your GP will be able to diagnose the cause and determine whether further investigation and treatment is needed.
Most cases of fainting aren't a cause for concern and don't require treatment, but you should see your GP if you're at all concerned.
You should also see your doctor after fainting if you:
During an assessment, your doctor will ask about your fainting episodes and your recent medical history. They may also measure your blood pressure and listen to your heartbeat using a stethoscope.
If your doctor thinks your fainting episode may have been caused by a heart problem, they may suggest that you have an electrocardiogram (ECG) .
An ECG records your heart's rhythm and electrical activity. A number of small, sticky patches called electrodes are placed on your arms, legs and chest. Wires connect the electrodes to an ECG machine.
Every time your heart beats, it produces tiny electrical signals. The ECG machine traces these signals on paper, recording any abnormalities in your heartbeat.
An ECG is usually carried out at a hospital or doctor surgery. The procedure is painless and takes about five minutes.
If your doctor thinks your fainting episode was associated with carotid sinus syndrome, they may massage your carotid sinus to see whether it makes you feel faint or lightheaded.
The carotid sinus is a collection of sensors in the carotid artery, which is the main artery in your neck that supplies blood to your brain.
If the carotid sinus massage causes symptoms, it may indicate that you have carotid sinus syndrome – see causes of fainting for more information.
Blood tests may be carried out to rule out conditions such as diabetes or anaemia , a condition where the body doesn't produce enough oxygen-rich red blood cells.
Your doctor may measure your blood pressure while you're lying down and again after you stand up. You may have orthostatic hypotension if your blood pressure falls after you stand up.
If you have orthostatic hypotension, you may be asked further questions to help determine the cause. For example, it can sometimes occur as a side effect of taking some medications.
If tests reveal an underlying cause of your fainting, such as a heart problem or orthostatic hypotension, your doctor may recommend treatment for fainting .
If someone you're with has fainted and they haven't regained consciousness within one or two minutes, put them into the recovery position .
After putting them into the recovery position, emergency services, ask for an ambulance, and stay with them until medical help arrives.
When you visit the doctor after a fainting episode, they'll investigate the type of fainting you experienced and whether there's an underlying cause.
If an underlying cause is found, treating it should help prevent further fainting episodes.
Read more about diagnosing fainting .
Most fainting episodes are associated with a temporary malfunction of the autonomic nervous system, which regulates the body's automatic functions, such as heartbeat and blood pressure.
This type of fainting is called neurally mediated syncope . Treatment for neurally mediated syncope involves avoiding any possible triggers.
If you're not sure what caused your fainting episode, your doctor may suggest keeping a diary of any symptoms you experience.
It may help to identify possible causes by making a note of what you were doing at the time you fainted.
There are also steps you can take to avoid losing consciousness if you think you may be about to faint.
Fainting can occur when an external trigger, such as a stressful situation, causes a temporary malfunction in your autonomic nervous system. This is called vasovagal syncope.
In most cases of vasovagal syncope, further treatment isn't required. However, you may find it useful to avoid potential triggers, such as stress or excitement, hot and stuffy environments, and long periods spent standing.
If you know injections or medical procedures like blood tests make you feel faint, you should tell the doctor or nurse beforehand. They'll make sure you're lying down during the procedure.
Fainting can occur when a bodily function or activity – such as coughing – places a sudden strain on the autonomic nervous system. This is called situational syncope.
There's no specific treatment for situational syncope, but avoiding the triggers may help. For example, if coughing caused you to faint, you may be able to suppress your urge to cough and avoid fainting.
Carotid sinus syndrome is where pressure on your carotid sinus causes you to faint. It's more common in older men.
Your carotid sinus is a collection of sensors in the carotid artery, which is the main artery in your neck that supplies blood to your brain.
You can avoid fainting by not putting any pressure on your carotid sinus – for example, by not wearing shirts with tight collars.
In some people, carotid sinus syndrome can be treated by having a pacemaker fitted. A pacemaker is a small electrical device that's implanted in your chest to help keep your heart beating regularly.
Fainting can occur when your blood pressure drops as you stand up. This drop in blood pressure is called orthostatic hypotension .
Avoiding anything that lowers your blood pressure should help prevent fainting. For example, avoid becoming dehydrated by increasing your fluid intake.
Your doctor may also advise you to eat small, frequent meals rather than large ones, and increase your salt intake.
Taking certain medications can also decrease blood pressure. However, don't stop taking a prescribed medication unless your doctor or another qualified healthcare professional in charge of your care advises you to do so.
Read more about treating low blood pressure .
Physical counterpressure manoeuvres are movements designed to raise your blood pressure and prevent you losing consciousness.
One study found training in physical counterpressure manoeuvres can reduce fainting in some people.
Physical counterpressure manoeuvres include:
You need to be trained to carry out these movements correctly. You can then do them if you experience any symptoms that suggest you're about to faint, such as feeling lightheaded.
If you've fainted, it could affect your ability to drive. Depending on what caused you to faint and whether you have any underlying health conditions, you may need to inform local driving authorities.
If you've fainted, it may affect your safety at work or the safety of others. For example, continuing to operate machinery may be dangerous if it's likely you'll faint again.
The healthcare professionals who diagnose and treat your condition can tell you whether it's likely to affect your work. If it is, speak to your health and safety representative.
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.