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"Fainting" What causes it?

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 lightheaded or dizzy before fainting.

A longer, deeper state of unconsciousness is often called a coma.

Considerations Return to top

When you faint, you not only experience loss of consciousness, but also loss of muscle tone and paling of color in your face. 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.

Causes Return to top

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.

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