Fainting is a brief loss of consciousness due to a drop in blood flow to the brain. The episode lasts less than a couple of minutes and you recover from it quickly and completely. You may feel light-headed or dizzy before fainting.
A longer, deeper state of unconsciousness is often called a coma.
When you faint, you not only lose consciousness, but you also lose muscle tone and the color in your face (pallor). You may also feel weak or nauseated just before fainting. You may have the sense that noises are fading into the background.
Fainting may occur while you:
Fainting can also be related to:
Other causes of fainting:
Less common but more serious reasons for fainting include heart disease (such as abnormal heart rhythm or heart attack) and stroke. These conditions are more likely in persons over age 65 and less likely in those younger than 40.
If you have a history of fainting, follow your doctor's instructions for how to prevent fainting episodes. 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 health care provider before having a blood test and make sure that you are lying down when the test is done.
You can take immediate treatment steps when someone has fainted:
Call 911 if the person who fainted:
Even if it's not an emergency situation, you should be seen by a doctor 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 health care provider will ask you questions to determine whether you simply fainted, or if something else happened (like a seizure or heart rhythm disturbance), and to figure out the cause of the fainting episode. If someone witnessed the fainting episode, their description of the event may be very helpful.
The questions will include:
The physical examination will focus on your heart, lungs, and nervous system. Your blood pressure may be measured in several different positions. People with a suspected arrhythmia may need to be admitted to a hospital for testing.
Tests that may be performed include:
Passed out; Light-headedness - fainting; Syncope; Vasovagal episode
Calkins H, Zipes DP. Hypotension and syncope. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 42.
Simon RP. Syncope. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 427.
Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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