Fainting is a brief loss of consciousness due to a drop in blood flow to the brain. The episode most often lasts less than a couple of minutes and you usually recover from it quickly. The medical name for fainting is syncope.
Passed out; Lightheadedness - fainting; Syncope; Vasovagal episode
When you faint, you not only lose consciousness, you also lose muscle tone and the color in your face. Before fainting, you may feel weak, sweaty, or nauseated. You may have the sense that your vision is constricting (tunnel vision) or noises are fading into the background.
Fainting may occur while or after you:
Fainting can also be related to:
Other causes of fainting, some of which may be more serious, include:
If you have a history of fainting, follow your health care provider's instructions for how to prevent fainting. For example, if you know the situations that cause you to faint, avoid or change them.
Get up from a lying or seated position slowly. If having blood drawn makes you faint, tell your provider before having a blood test. Make sure that you are lying down when the test is done.
You can use these immediate treatment steps when someone has fainted:
Call 911 or the local emergency number if the person who fainted:
Even if it is not an emergency situation, you should be seen by a provider if you have never fainted before, if you faint often, or if you have new symptoms with fainting. Call for an appointment to be seen as soon as possible.
Your provider will ask questions to determine whether you simply fainted, or if something else happened (such as a seizure or heart rhythm disturbance), and to figure out the cause of the fainting episode. If someone saw the fainting episode, their description of the event may be helpful.
The physical exam will focus on your heart, lungs, and nervous system. Your blood pressure may be checked while you are in different positions, such as lying down and standing. People with a suspected arrhythmia may need to be admitted to a hospital for testing.
Tests that may be ordered include:
Treatment depends on the cause of fainting.
Calkins H, Zipes DP. Hypotension and syncope. In: Zipes DP, Libby P, Bonow RO, Mann DL, Tomaselli GF, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 11th ed. Philadelphia, PA: Elsevier; 2019:chap 43.
De Lorenzo RA. Syncope. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier; 2018:chap 12.
Walsh K, Hoffmayer K, Hamdan MH. Syncope: diagnosis and management. Curr Probl Cardiol. 2015;40(2):51-86. PMID: 25686850 pubmed.ncbi.nlm.nih.gov/25686850/.