Fainting Symptoms But Didn't Faint

Mechanical problems with the heart can also cause presyncope when the body needs more blood than the heart can pump. These structural diseases include aortic stenosis, which is a heart valve condition, and hypertrophic cardiomyopathy, which is the enlargement of heart muscle cells and the thickening of the heart chamber walls.

What Is Presyncope?

Prescyncope is when you feel as if you’re about to pass out, but you don’t actually faint. It’s sometimes referred to as near syncope. You may also feel lightheaded, sweaty, nauseous, warm, and weak, or have a fast heartbeat or blurry vision.

Presyncope can be caused by the same factors that cause syncope. This is when you actually pass out and later regain consciousness. Some of these factors are harmless, but others can be dangerous, even life-threatening.

What Causes Presyncope?

Presyncope happens when the amount of blood flowing to your brain temporarily decreases. Numerous medical conditions can cause presyncope. Presyncope can be one of the following types.

Vasovagal. This type of presyncope is caused by a drop in blood flow to your brain due to low blood pressure. This is the most common cause of syncope and presyncope. It’s usually caused by a combination of being dehydrated and standing or sitting up too quickly. Vasovagal presyncope can also have emotional triggers such as:

Getting a shot
Having blood drawn
Seeing blood
Standing up too quickly
Standing for too long
Unexpected trauma, pain, or stress

Situational presyncope is another type of vasovagal presyncope. This occurs when you have a reflex response to a specific trigger. Your heart may slow or your blood vessels may widen. This causes a drop in your blood pressure, decreasing blood flow to your brain. Some additional situational triggers can include:

Dehydration
Fear
Hunger
Urinating, called post-micturition presyncope
Eating
Lifting something heavy

Orthostatic hypotension. This is also a type of vasovagal syncope or presyncope. When you stand, your blood vessels normally get smaller to keep blood from collecting in your legs. This doesn’t happen in people with orthostatic hypotension. Instead, they experience a drop in blood pressure when they stand, which can cause presyncope.

Cardiac. If your heart beats too fast, this is called tachycardia. If it beats too slow, this is called bradycardia. Both can cause presyncope or syncope. Other types of heart arrhythmias, or abnormal rhythms, can also cause presyncope.

Cardiac presyncope or syncope can be caused by problems with a pacemaker. They might also indicate a tear in the large artery that carries blood to the rest of your body. A narrowing of the valve between your aorta and heart might also cause you to feel faint.

Neurologic. Neurologic presyncope can be caused by conditions such as a stroke or seizure. It can also result from a transient ischemic attack (TIA), which is a brief stroke that only lasts a few minutes. Other, less common causes of neurologic presyncope include migraines and normal pressure hydrocephalus (NPH), which is a type of brain disorder.

Postural orthostatic tachycardia syndrome (POTS). This is a rare disorder that affects your blood flow. It most commonly occurs in women from ages 13 to 50. It happens when your heart rate increases by at least 30 beats per minute when you stand. It causes other symptoms when you stand such as presyncope and tiredness. POTS can also cause palpitations, which is when your heart feels like it’s beating too hard or too fast.

How Common is Presyncope?

It’s hard to know how common presyncope is because information about it is not usually included in reports of syncope. Presyncope is likely more common than syncope. At some point, 19% of people in the United States will experience an episode of syncope. Additionally:

58% of people who experience syncope are female.
3% of emergency department visits are for syncope.
6% of hospitalizations are from syncope.
Most episodes of syncope occur either in early adulthood or after the age of 70.

One study that focused on presyncope showed that:

The average age of patients was 56.
61% of patients were female.
49% of patients were admitted to the hospital, compared with 69% of syncopal patients.
20% of patients required medical assistance or had an adverse outcome.

How Is Presyncope Diagnosed?

It’s important to talk to your doctor if you have presyncope symptoms to rule out a serious condition. Your doctor will listen to your symptoms and do a physical examination. You may need other tests as well, which could include:

Tilt table test, which measures your blood pressure and heart rate at various positions, from lying flat to upright on a special table
Electrocardiogram, which measures the electrical rhythm of your heart
Exercise stress test, which is an electrocardiogram done while you’re exercising strenuously
Echocardiogram, which is an ultrasound of the heart
Electrophysiology study, which is a test used to diagnose problems with your heart’s rhythm
Holter monitor, which is a vest that you wear that continuously performs an electrocardiogram over 1 to 7 days
Event monitor, which is an electrocardiogram that you wear for 1 to 2 months

How Is Presyncope Treated?

The treatment for presyncope will depend on the cause and may include:

Being careful when you stand up
Raising the head of your bed while you’re sleeping
Medications
Discontinuing or changing existing medications
Avoiding the situations that cause your presyncope
Treating any heart conditions you may have
A pacemaker, if needed
Wearing compression stockings to help your circulation
Changing your diet, which may mean consuming more salt or potassium, eating smaller meals more frequently, drinking more fluids, or avoiding caffeine and alcohol

Show Sources

American Family Physician: “Syncope: Evaluation and Differential Diagnosis.”

Cleveland Clinic: “Postural Orthostatic Tachycardia Syndrome (POTS),” “Syncope.”

JOHNS HOPKINS: “Syncope (Fainting).”

Fainting

Fainting, also called passing out or syncope, is a temporary loss of consciousness. It’s caused by a sudden decrease of blood flow to the brain. An episode typically lasts a few seconds or minutes. Most fainting spells are not a cause for concern. But if you faint often or have other symptoms, you should seek medical attention.

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Overview

What is fainting?

Fainting is when you lose consciousness for a short time. It’s caused by a sudden drop in blood flow to the brain. A fainting episode usually lasts a few seconds or minutes, then the person wakes up and returns to normal.

Fainting is also called:

Decreased consciousness.
Loss of consciousness.
Passing out.
Syncope.

Are there warning signs of passing out?

Before fainting, you might feel:

Cold and clammy.
Dizzy.
Lightheaded.
Hot and suddenly sweaty.
Nauseous.
Stressed out or anxious.
Weak.

In addition, you may:

Fall down.
Get a headache.
Have vision changes (“white out,” “black out” or “see stars”).
Hear ringing in your ears.
Lose control of your muscles.

Possible Causes

What are the most common causes of fainting?

Fainting is usually not a sign of a serious health problem, but it can be.

The most common reason for fainting is a sudden drop in blood pressure, which reduces blood flow and oxygen to the brain. There are many reasons why a drop in blood pressure could lead to a temporary loss of consciousness:

Cardiac syncope: This type of syncope involves fainting due to a heart problem. Many heart conditions can affect how much oxygenated blood is pumped to the brain.
Carotid sinus syncope: This type of syncope can happen when the carotid artery in the neck is constricted (pinched). The carotid artery is a blood vessel that supplies the brain. This type of fainting can occur when someone wears a very tight collar, stretches or turns the neck too much, or has a bone in the neck that is pinching the artery.
Situational syncope: Certain bodily movements or functions can naturally cause a drop in blood pressure that may lead to fainting spells. Examples include when a person pees, poops, coughs or stretches.
Vasovagal syncope: This can occur when a person experiences a stressful event. Examples include the sight of blood, emotional stress, physical or emotional trauma, or pain. The stressful event stimulates a bodily reflex called the vasovagal reaction. The heart slows down and pumps less blood, so blood pressure drops. Then the brain doesn’t get enough oxygenated blood, and the person faints.

Are there other reasons why I fainted?

Other possible causes of passing out include:

Certain medications such as diuretics (water pills), calcium channel blockers and angiotensin-converting enzyme (ACE) inhibitors (often used for high blood pressure). Other examples include nitrates for heart disease, antipsychotics for mental health disorders, antihistamines for allergies and narcotics for pain.
Dehydration or overheating.
Neurologic condition, such as a seizure disorder, although this is rare.
Sudden drop in blood sugar, as may happen in a person with diabetes.

Activities that may cause you to pass out include:

Skipping too many meals.
Hyperventilating (breathing too fast).
Working, playing or exercising too hard, especially in the heat.
Standing up too quickly.
Using alcohol, marijuana or illegal drugs.

Care and Treatment

What should I do if someone faints?

If someone loses consciousness:

Make sure the person’s airway is clear.
Check that the person is breathing.
Check that the heart is beating.
Call 911 or seek immediate medical attention if needed.

When someone faints and then wakes up:

Encourage them to sit down or lie down for 10 to 15 minutes (sometimes longer, until symptoms pass).
Check for any injuries that might need medical attention (such as a head injury or a cut).
Suggest that they sit forward and lower their head below their shoulders and knees.
Offer ice or cold water.

Can I prevent fainting?

Pay attention to specific activities or situations that trigger fainting. When you know what causes your fainting spells, you can take steps to avoid them. For example, if getting up too quickly sometimes makes you pass out, learn to take your time standing.

If you notice how you feel just before you faint, you can try certain strategies to prevent it:

Make a fist.
Tense your arms.
Cross your legs.
Squeeze your thighs together.

When to Call the Doctor

When should I discuss fainting with my doctor?

If you faint once and are in good health otherwise, you probably don’t need to talk to a healthcare provider. But seek medical attention if you:

Are injured due to a fainting fall.
Have repeat, frequent fainting spells.
Take longer than a few minutes to regain consciousness.

Talk to a healthcare provider if you pass out and have any of the following symptoms:

Blurry vision.
Chest pain.
Confusion or trouble talking.
Irregular heartbeat.
Loss of control with peeing or pooping.
Shortness of breath.

Also report any loss of consciousness to a healthcare provider if you:

Are pregnant.
Have diabetes.
Have a problem with your heart or blood pressure.

A note from Cleveland Clinic

Fainting, or passing out, is usually caused by a drop in blood pressure, which reduces blood flow and oxygen to the brain. Most fainting spells are nothing to worry about. But talk to a healthcare provider if you lose consciousness repeatedly or have any other symptoms.

Last reviewed by a Cleveland Clinic medical professional on 08/06/2021.

References

American Academy of Family Physicians. Fainting. (https://familydoctor.org/condition/fainting/?adfree=true) Accessed 9/2/2021.
Mizrachi EM, Sitammagari KK. Cardiac Syncope. (https://www.ncbi.nlm.nih.gov/books/NBK526027/) [Updated 16 April 2021]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. Accessed 9/2/2021.
Momodu II, Okafor CN. Orthostatic Syncope. (https://www.ncbi.nlm.nih.gov/books/NBK537285/) [Updated 15 Feb 2021]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. Accessed 9/2/2021.
National Institute of Neurological Disorders and Stroke. Syncope Information Page. (https://www.ninds.nih.gov/Disorders/All-Disorders/Syncope-Information-Page) Accessed 9/2/2021.
U.S. National Library of Medicine. Fainting. (https://medlineplus.gov/fainting.html) Accessed 9/2/2021.

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Fainting symptoms without fainting: What to know

When a person has fainting symptoms but does not actually faint, it is known as presyncope. Presyncope is the stage before fainting, which can make someone feel lightheaded, weak, warm, sweaty, or nauseous. Heart palpitations and blurry vision may also occur.

Noncardiac presyncope

This is the most common type of presyncope. It includes vasovagal presyncope, which occurs because of the vagus nerve. This is a large nerve that runs from behind the throat down through the abdomen.

If the vagus nerve becomes overactive, it can result in low blood pressure, reducing blood flow to the brain. A common cause of this is orthostatic intolerance. This is where a person experiences symptoms, such as dizziness, from standing due to insufficient blood flow.

A person experiences orthostatic hypotension when their blood pressure reduces by at least 20 millimeters of mercury (mm Hg) systolic, or 10 mm Hg diastolic, within 3 minutes of standing or sitting up.

Some factors that make presyncope more likely include:

dehydration
bed rest in older adults
certain medications, such as those that affect blood pressure or fluid levels
underlying conditions, such as those that affect the nervous system

In some people, stress or strong emotions can also trigger presyncope.

Cardiac presyncope

Presyncope can occur due to mechanical problems with the heart, or an irregular heart rhythm. If this is the case, presyncope could signify a more serious condition.

An irregular heart rhythm can stop the heart from pumping enough blood around the body, including to the brain. Both slow and fast heart rates can lead to presyncope or syncope.

Mechanical problems with the heart can also cause presyncope when the body needs more blood than the heart can pump. These structural diseases include aortic stenosis, which is a heart valve condition, and hypertrophic cardiomyopathy, which is the enlargement of heart muscle cells and the thickening of the heart chamber walls.

A person with cardiac presyncope may experience palpitations. It can happen while they are sitting, lying down, or exercising.

To diagnose presyncope, a doctor will ask about a person’s symptoms, review their medical history and any medications they take, and perform a physical examination.

If someone has symptoms when they stand up too fast, the doctor may ask them to sit down and stand up to see if they have orthostatic intolerance.

As there are many causes of presyncope, a doctor may first try to rule out life threatening causes. This may involve tests to check the function of the heart, such as an echocardiogram.

Other tests may include:

a finger stick glucose test
blood tests to measure blood cell counts, electrolytes, lactate, and cardiac enzymes
CT scans of the head

Treatment for presyncope varies depending on the cause and severity of symptoms. For example, it could involve fluids and rest for dehydration, or medication or dosage changes for side effects of drugs.

A doctor may also suggest physical counter-pressure maneuvers to stop the symptoms. A 2020 systematic review suggests that this way of moving a person’s body into different positions could stop them from fainting during an episode of presyncope.

Examples of these body movements include:

leg crossing with muscle tensing
squatting
arm tensing
isometric handgrip
neck flexion

If the cause is harder to identify or presyncope keeps happening, doctors will need to investigate further. If they believe a person is at risk of adverse outcomes, they may decide to admit the individual to the hospital.

Doctors can use the Boston syncope criteria to help them make this decision. The criteria list risk factors for serious illness, such as:

symptoms of acute coronary syndrome, which causes a sudden reduction in blood flow to the heart
history of heart or heart valve disease
family history of sudden death
signs of conduction disease, which refers to dysfunction of the electrical system controlling heart rate and rhythm
persistently atypical vital signs, such as high or low body temperature, breathing rate, pulse, and blood pressure
extreme volume depletion, or a loss of fluid in the space outside of the cells in the body

The symptoms of presyncope, such as feeling lightheaded, hot, or weak, can be similar to those of other conditions. Other things that may cause these symptoms include:

A doctor will be able to test for or rule out these other explanations.

Presyncope occurs when a person feels like they are about to faint but do not actually lose consciousness. Someone with presyncope may experience lightheadedness, weakness, excessive sweating, and heart palpitations.

There are many potential causes of presyncope. Most are relatively mild and treatable, but if the cause is heart-related, a person may need to go to the hospital.

Because the causes of presyncope vary so much in severity, it is essential that people who are experiencing presyncope contact a doctor.

Last medically reviewed on December 13, 2022

Vascular
Blood / Hematology
Cardiovascular / Cardiology
Neurology / Neuroscience

How we reviewed this article:

Medical News Today has strict sourcing guidelines and draws only from peer-reviewed studies, academic research institutions, and medical journals and associations. We avoid using tertiary references. We link primary sources — including studies, scientific references, and statistics — within each article and also list them in the resources section at the bottom of our articles. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Description of recommended physical counterpressure maneuvers. (n.d.).
https://cpr.heart.org/en/resuscitation-science/first-aid-guidelines/first-aid/description-of-recommended-physical-counterpressure-maneuvers
Jeanmonod, R., et al. (2022). Vasovagal episode.
https://www.ncbi.nlm.nih.gov/books/NBK470277/
Jensen, J. L., et al. (2020). Immediate interventions for presyncope of vasovagal or orthostatic origin: A systematic review [Abstract].
https://pubmed.ncbi.nlm.nih.gov/30957664/
Momodu, I. I., et al. (2022). Orthostatic syncope.
https://www.ncbi.nlm.nih.gov/books/NBK537285/
Roncon, L., et al. (2018). Impact of syncope and pre-syncope on short-term mortality in patients with acute pulmonary embolism [Abstract].
https://pubmed.ncbi.nlm.nih.gov/29655808/
Whitledge, J. D., et al. (2022). Presyncope.
https://www.ncbi.nlm.nih.gov/books/NBK459383/

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Fainting Symptoms But Didn’t Faint

What Is Presyncope?

What Causes Presyncope?

How Common is Presyncope?

How Is Presyncope Diagnosed?