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Fainting is loss of consciousness caused by a temporary lack of oxygen to the brain. Known by the medical term "syncope," fainting may be preceded by dizziness, nausea, or a feeling of extreme weakness.


When a person faints, the loss of consciousness is brief. The person will wake up as soon as normal blood flow is restored to the brain. Blood flow is usually restored by lying flat for a short time. This position puts the head on the same level as the heart so that blood flows more easily to the brain.
A fainting episode may be completely harmless and of no significance, but it can be a symptom of a serious underlying disorder. No matter how trivial it seems, a fainting episode should be treated as a medical emergency until the cause is determined.

Causes and symptoms

Extreme pain, fear, or stress may bring on fainting. This type of fainting is caused by overstimulation of the vagus nerve, a nerve connected to the brain that helps control breathing and circulation. In addition, a person who stands still or erect for too long may faint. This type of fainting occurs because blood pools in the leg veins, reducing the amount that is available for the heart to pump to the brain. This type of fainting is quite common in older people or those taking drugs to treat high blood pressure.
When an older person feels faint upon turning the head or looking upward suddenly, the cause could be osteoarthritis of the neck bones. Osteoarthritis damages the cartilage between the neck bones and causes pressure on blood vessels leading to the brain.
Fainting can be a symptom of a disease such as Stokes-Adams syndrome, a condition in which blood flow to the brain is temporarily reduced because of an irregular heartbeat. Some people may experience fainting associated with weakness in the limbs or a temporary problem in speaking caused by obstructed blood flow in vessels passing through the neck to the brain. Pregnant women frequently feel faint. Fainting may also occur as a result of low blood sugar. Low blood sugar can occur if a person skips a meal or has diabetes.
Fainting can also be caused by:
  • prolonged coughing
  • straining to defecate or urinate
  • blowing a wind instrument too hard
  • remaining in a stuffy environment with too little oxygen
Sometimes fainting may be caused by a temporary drop in the blood supply to the brain caused by a transient ischemic attack (TIA). A TIA, sometimes called a mini-stroke, is a disruption in the blood supply to the brain caused by a blocked or burst blood vessel. Seek help immediately if a fainting spell is followed by one or more of the symptoms listed below:
  • numbness or tingling in any body part
  • blurred vision
  • confusion
  • difficulty speaking
  • loss of movement in arms or legs
A few seconds before fainting, a person may sweat or become pale, feel nauseated or dizzy, and have blurred vision or racing heartbeat. Once the person loses consciousness, the pupils may dilate as the heart
If a person is feeling faint, unconsciousness may be prevented by sitting with the head between the knees, as shown in the illustration above, or by lying flat with the legs raised.
If a person is feeling faint, unconsciousness may be prevented by sitting with the head between the knees, as shown in the illustration above, or by lying flat with the legs raised.
(Illustration by Electronic Illustrators Group.)
rate slows down. There may be abnormal movements. Muscles may tighten or the back may arch. These movements do not last long and they are not violent.
In most cases, the patient regains consciousness within a few minutes, but the fainting spell may be followed by nervousness, headache, nausea, dizziness, pallor or sweating. The person may faint again, especially if he or she stands up within 30 minutes.


Most episodes of fainting are a one-time occurrence. When a person experiences repeated fainting spells, a physician should be consulted.


Most of the time, a person who faints ends up lying on the floor. If this happens, the patient should be rolled onto his or her back. Because someone who faints often vomits, bystanders should keep the airway open. A person who is fainting should not be held upright or in a sitting position. These positions prevent blood flow to the brain and may bring on a seizure.
Bystanders should check the patient's breathing and pulse rate. The pulse may be weak and slow. If there are no signs of breathing or heart rate, the problem is more serious than fainting, and cardiopulmonary resuscitation (CPR) must begin.
If breathing and pulse rates seem normal, the person's legs should be raised above the level of the head so that gravity can help the blood flow to the brain. Belts, collars or any other constrictive clothing should be loosened.
If the person does not regain consciousness within a minute or two after fainting, medical help should be summoned.


After a fainting spell, the person should regain normal color but may continue to feel weak for a short time. Lying down quietly for a few moments may help.
In most cases, an attack of fainting is not serious. As soon as the underlying pain or stress passes, the danger of repeated episodes also is eliminated.


If a person is feeling faint, unconsciousness may be prevented by sitting with the head between the knees or lying flat with the legs raised.
A person who has fainted should lie flat for 10-15 minutes after regaining consciousness to give the system a chance to regain its balance. Standing up too soon may bring on another fainting spell.



Greenberg, David A., et al. Clinical Neurology. 2nd ed. Norwalk, CT: Appleton & Lange, 1993.

Key terms

Osteoarthritis — A disease characterized by damage to the cartilage in the joints. The joints become inflamed, deformed, and enlarged, and movement becomes painful.
Stokes-Adams syndrome — Recurrent episodes of temporary loss of consciousness (fainting) caused by an insufficient flow of blood from the heart to the brain. This syndrome is caused by a very rapid or a very slow heartbeat.
Transient ischemic attack (TIA) — A brief interruption of the blood supply to part of the brain that causes a temporary impairment of vision, speech, or movement. Usually, the episode lasts for just a few moments, but it may be a warning sign for a full-scale stroke.
Vagus nerve — A cranial nerve, that is, a nerve connected to the brain. The vagus nerve has branches to most of the major organs in the body, including the larynx, throat, windpipe, lungs, heart, and most of the digestive system.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


Temporary loss of consciousness due to brain deprivation of an adequate supply of blood and thus oxygen and glucose. This results from a reduction in blood pressure, either because the heart is pumping too slowly or less efficiently or because the arteries of the body have widened. If a fainting person is allowed to lie and the legs raised, recovery will be rapid. It is dangerous to keep a fainting person upright.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

Patient discussion about fainting

Q. i am 12 and my hair is falling out what do i do? there is like a hair ball in my tub

A. First of all you are going through puberty and the hormonal levels in your body are changing, this could cause accelerated hair loss that will go away. However, if you feel like you are having severe hair loss you should go and get blood tests for the evaluation of several vitamin defficiencies (B12, Folic acid and Iron), that can be the reason. Soemtimes a lack in our nutrition can be the reason for losing hair.

Q. I found out 1week ago i was 6wks pregnant and lastnight i passed a 1/2dollar size clear ball did i miscarrie? the ball was clear,soft and jellie like and it came w/a lot of blood but i didnt see no signs of a baby or anything like that

A. Possibly, but not essentially. In this age the embryo is quite small (several millimeters), so you may easily mistaken it. My best advice is to consult a doctor (e.g. gynecologist) so an US or other test can be done to accurately diagnose a miscarriage.

Take care,

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