Fainting is a temporary loss of consciousness due to a drop in blood flow to the brain. The episode is brief (lasting less than a couple of minutes) and is followed by rapid and complete recovery. 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 experience loss of consciousness, but also loss of muscle tone and paling of color in your face (pallor). You may also feel weak or nauseated just prior to fainting, and you may have the sense that surrounding noises are fading into the background.

Fainting may occur while you are urinating, having a bowel movement (especially if straining), coughing very hard, or when you have been standing in one place too long. Fainting can also be related to fear, severe pain, or emotional distress.

A sudden drop in blood pressure can cause you to faint. Your blood pressure may drop suddenly if you are bleeding or severely dehydrated. It can also happen if you stand up very suddenly from a lying position.

Certain medications may lead to fainting by causing a drop in your blood pressure or for another reason. Common drugs that contribute to fainting include those used for anxiety, high blood pressure, nasal congestion, and allergies.

Other reasons you may faint include hyperventilation, drug or alcohol use, and low blood sugar.

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 and have been seen by a medical professional, 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. Avoid sudden changes in posture. 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:

• Check the person's airway and breathing. If necessary, call 911 and begin rescue breathing and CPR.
• Loosen tight clothing around the neck.
• Raise the person's feet above the level of the heart (about 12 inches).
• If vomiting has occurred, turn the person onto their side to prevent choking.
• Keep the person lying down for at least 10 - 15 minutes, preferably in a cool and quiet space. If this is not possible, sit the person forward and place their head between their knees.

Call 911 if the person who fainted:

• Fell from a height, especially if injured or bleeding
• Does not become alert quickly (within a couple of minutes)
• Is pregnant
• Is over age 50
• Has diabetes (check for medical identification bracelets)
• Feels chest pain, pressure, or discomfort
• Has a pounding or irregular heartbeat
• Has a loss of speech, visual disturbances, or inability to move one or more limbs
• Has convulsions, tongue injury, or loss of bladder or bowel control

Even if it's not an emergency situation, people should be seen by a doctor if they have never fainted before, if they are fainting frequently, or if they have new symptoms associated with fainting. Call for an appointment to be seen as soon as possible.

When you see your doctor, the focus of the questions will be 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.

The questions will include:

• Is this the first time you have fainted?
• When did you faint? What were you doing before it occurred? For example, were you going to the bathroom, coughing, or standing for a long time?
• How would you describe the dizziness that you felt before fainting? Did you feel light-headed, off-balance, or like the room was spinning?
• Was the faint associated with convulsions (jerking muscle movements), tongue trauma, or loss of control of your bowels?
• When you regained consciousness were you aware of your surroundings or were you confused?
• Did you experience chest pain or heart palpitations before you fainted?
• Does fainting occur when you change positions -- for example, go from lying to standing?

The physical examination will focus on your heart, lungs, and nervous system. Your blood pressure may be measured in several different positions.

Tests that may be performed include:

• ECG
• Holter monitor
• X-ray of the chest
• Echocardiogram
• EEG
• Blood tests for anemia or body chemical imbalances

Simon RP. Syncope. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 427.