Definition

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.

Causes

In general, fainting is caused by decreased blood flow to the brain.

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:

  • During medical procedures
  • During times of high stress, trauma, or fright
  • After standing still for a long period of time

Medical conditions:

Fainting can also occur as a side effect to medications. These include:

  • Blood pressure medications
  • Medications to regulate heart rhythms
  • Diuretics
  • Certain antidepressants

Risk Factors

Factors that increase your risk of fainting include having a history of fainting.

Symptoms

Symptoms may include:

  • Sudden loss of consciousness
  • Inability to remain standing or sitting
  • Consciousness regained without any need for intervention
  • Lightheadedness before losing consciousness

When Should I Call My Doctor?

Call your doctor if you are having episodes of fainting. This is especially important if you:

  • Have a heart condition
  • Have a job where you or others may be at risk if you faint. Examples include airline pilot, bus driver, or machinist.

When Should I Call for Medical Help Immediately?

Call for emergency medical services right away if you have:

  • Weakness or numbness of face, arm, or leg, especially on the left side of the body
  • Confusion
  • Loss of balance, coordination problems
  • Vision problems
  • Severe headache
  • Rapid, irregular heartbeat; chest pain

Diagnosis

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).

Images may be taken of your blood flow. This can be done with MR angiogram and CT angiogram.

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

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.

Prevention

Decreasing the risk of fainting will depend on the cause. Some factors that may help include:

  • Rising slowly and carefully from lying down. Start by sitting up for a minute and then stand up.
  • Drinking plenty of fluids.
  • Discussing helpful dietary changes with your doctor. This may include eating smaller, more frequent meals throughout the day.
  • Avoiding alcohol or other drugs.

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:

  • Crossing your legs while tensing the muscles of legs, abdomen, and buttocks.
  • Forcefully squeezing a rubber ball or other object as hard as possible.
  • Gripping one hand with the other while tensing both arms and raising the elbows slightly.
RESOURCES:

American Heart Association
http://www.heart.org

Family Doctor—American Academy of Family Physicians
http://familydoctor.org

CANADIAN RESOURCES:

Alberta Health
http://www.health.alberta.ca

Health Canada
https://www.canada.ca

REFERENCES:

Benditt D, Goldstein M. Fainting. American Heart Association, Circulation website. Available at: http://circ.ahajournals.org/content/106/9/1048.full. Published 2002. Accessed February 16, 2018.

Chen LY, Benditt DG, et al. Management of syncope in adults: an update. Mayo Clin Proc. 2008;83(11):1280-1293.

Choosing wisely. EBSCO DynaMed website. Available at:http://www.dynamed.com/topics/dmp~AN~T905359/Choosing-Wisely. Updated July 23, 2015. Accessed February 16, 2018.

Fainting. Family Doctor—American Academy of Family Physicians website. Available at: http://familydoctor.org/familydoctor/en/diseases-conditions/fainting.html. Updated December 2017. Accessed February 16, 2018.

Miller TH, Kruse JE. Evaluation of syncope. Am Fam Physician. 2005;72(8):1492-1500.

Syncope—approach to the patient. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T116050/Syncope-approach-to-the-patient. Updated February 14, 2018. Accessed February 16, 2018.

Vasovagal syncope. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T116865/Vasovagal-syncope. Updated October 23, 2018. Accessed February 16, 2018.

2/6/2007 DynaMed Plus Systematic Literature Surveillance. Available at:http://www.dynamed.com/topics/dmp~AN~T116865/Vasovagal-syncope: van Dijk N, Quartieri F, Blanc JJ, et al. Effectiveness of physical counterpressure maneuvers in preventing vasovagal syncope: the Physical Counterpressure Manoeuvres Trial (PC-Trial). J Am Coll Cardiol. 2006;48(8):1652-1657.

3/24/2015 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Mills PB, Fung CK, et al. Nonpharmacologic management of orthostatic hypotension: A systematic review. Arch Phys Med Rehab. 2015;96(20:366-375.

Last reviewed March 2018 by EBSCO Medical Review Board Rimas Lukas, MD  Last Updated: 3/24/2015