Fainting is a loss of consciousness that happens quickly and sometimes without warning. A fainting episode usually resolves within seconds to minutes. If fainting is caused by another condition, then the condition will need to be treated.
In general, fainting is caused by decreased blood flow to the brain.
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Decreased blood flow to the brain can be caused by:
Most commonly, vasovagal spells. Vasovagal spells can occur:
Fainting can also occur as a side effect to medications. These include:
Factors that increase your risk of fainting include having a history of fainting.
Symptoms may include:
Call your doctor if you are having episodes of fainting. This is especially important if you:
Call for emergency medical services right away if you have:
You will be asked about your symptoms and medical history. A physical exam will be done.
Your bodily fluids may be tested. This can be done with blood tests.
Your heart activity may be tested. This can be done with:
Your brain activity may be tested. This can be done with electroencephalogram (EEG).
Additional tests may be done. They may include a tilt table test.
If initial tests are unclear, brain images may be taken. This can be done with:
Treatment will depend on the underlying condition that has caused fainting. This may include medications, lifestyle changes, or surgery.
Knowing the warning signs of fainting can help prevent injury. If warning signs are present, the person should be encouraged to sit or lie down right away.
Decreasing the risk of fainting will depend on the cause. Some factors that may help include:
There are certain physical movements that rapidly increase blood pressure and blood flow to the brain. These movements may prevent fainting after warning signs appear. Examples of physical movements may include:
American Heart Association
Family Doctor—American Academy of Family Physicians
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Last reviewed March 2018 by EBSCO Medical Review Board Rimas Lukas, MD Last Updated: 3/24/2015