Fainting, or passing out, is a temporary loss of consciousness from a sudden decrease of blood flow to your brain. An episode usually lasts a few seconds or minutes. Most are harmless, but if you faint often or have other symptoms, you should seek medical attention.


What is fainting?

Fainting is a short-term loss of consciousness. It happens because of a sudden drop in blood flow to your brain. A fainting episode usually lasts a few seconds or minutes. Then, you wake up and return to normal.

Other names for fainting are:

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

Are there stages or different severity levels of fainting?

Signs you’re about to faint may include feeling:

  • Cold and clammy.
  • Dizzy.
  • Lightheaded.
  • Hot and suddenly sweaty.
  • Sick to your stomach.
  • Stressed out or anxious.
  • Weak.

In addition, you may:

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

For a few hours after fainting, you may feel tired or just not quite right.


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Possible Causes

What are the most common causes of fainting?

The most common reason for fainting is a sudden drop in blood pressure, which reduces blood flow and oxygen to your 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 because of a heart problem. Many heart conditions can affect how much oxygenated blood your heart can pump to your brain. This type makes up 15% of fainting incidents.
  • Carotid sinus syncope: This type of syncope can happen when something pinches or constricts the carotid artery in your neck. The carotid artery is a blood vessel that supplies your brain. This type of fainting can occur when someone wears a very tight collar, stretches or turns their neck too much, or has a bone in their neck that’s pinching their artery.
  • Vasovagal syncope: This can occur when a person experiences a stressful event. Examples include the sight of blood, emotional stress, physical trauma, emotional trauma or pain. The stressful event stimulates a bodily reflex called the vasovagal reaction. Your heart slows down and pumps less blood, so your blood pressure drops. Then, your brain doesn’t get enough oxygenated blood, and you faint. Certain bodily movements or functions also can naturally cause a drop in blood pressure that may lead to fainting spells. Examples include when a person pees, poops, coughs or stretches.

Other possible causes of fainting

You may faint because of:

  • Certain medications that treat high blood pressure, such as diuretics (water pills), calcium channel blockers and angiotensin-converting enzyme (ACE) inhibitors. Other examples include nitrates for heart disease, antipsychotics for mental health disorders, antihistamines for allergies and opioids for pain.
  • Dehydration or overheating.
  • A neurologic condition, such as a seizure disorder or stroke.
  • A sudden drop in blood sugar, as may happen in a person who has diabetes.
  • An unknown reason, which happens in up to 50% of fainting cases.

Activities that may cause you to faint

Things you do with your body that can make you faint 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

How is fainting treated?

A healthcare provider can work with you to determine the cause of your fainting. They can provide treatment if you need it.

People — often age 65+ — who faint when they stand up too quickly may need:

If a diagnosed heart issue made you faint, a provider may recommend:

People with carotid sinus syncope may need:

  • Medication.
  • Pacemaker.

If fainting isn’t a frequent problem, many people don’t need treatment beyond what you can provide yourself.

First aid for fainting

If someone loses consciousness:

  • Make sure the person’s airway is clear.
  • Check that the person is breathing.
  • Check that their heart is beating.
  • Call 911 or seek immediate medical attention if they’re hurt.
  • Start CPR if the person isn’t breathing or if you don’t feel a pulse.
  • Ask someone to look for an automated external defibrillator (AED) 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.

What are the possible complications or risks of not treating fainting?

Fainting can happen again in people who have untreated fainting causes.

People who faint because of low blood pressure when they stand up (orthostatic hypotension) may be at risk of injury from falling when they faint.

Cardiac syncope is a sign that you may have a heart issue that can be fatal. You may have an abnormal heart rhythm or an issue with a part of your heart, such as a valve. Without treatment, people who have cardiac syncope are at least twice as likely to have a car accident as the general population.


Can fainting be prevented?

Yes, you can prevent fainting when you know what causes you to faint. Pay attention to specific activities or situations that make you faint. For example, if getting up too quickly sometimes makes you faint, learn to take your time standing up. You can also move your legs to help your blood move before you stand up.

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

  • Make a fist with your hand.
  • Tense your arms.
  • Cross your legs.
  • Squeeze your thighs together.
  • Lie down.
  • Sit, lean forward and put your head between your knees.

When To Call the Doctor

When should fainting be treated by a doctor or healthcare provider?

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:

  • Have an injury from a fainting fall.
  • Faint while exercising.
  • Have repeat, frequent fainting spells.
  • Take longer than a few minutes to regain consciousness.

Fainting usually isn’t a sign of a serious health issue, but it can be. Talk to a healthcare provider if you faint and have any of the following symptoms:

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.
  • Have a family history of sudden death.

A note from Cleveland Clinic

Fainting, or passing out, usually happens because of a drop in blood pressure, which reduces blood flow and oxygen to your 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. Finding the cause can help you take action to prevent future fainting spells.

Medically Reviewed

Last reviewed on 03/14/2023.

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