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:
Call 911 if the person who fainted:
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:
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:
Passed out; Light-headedness - fainting; Syncope; Vasovagal episode