Fainting happens when your brain does not get enough oxygen. You lose consciousness, or "pass out," for a brief time (usually just a few seconds or minutes).
Fainting, which is also called syncope, can be caused by many different things. Sometimes a specific cause for fainting cannot be found.
A sudden drop in your blood pressure can cause you to faint. Sometimes your heart rate and blood vessels can't react fast enough when your body's need for oxygen changes. This is very common among older people and in people who have certain health conditions, such as diabetes. Fainting can happen when:
Coughing, urinating and stretching can also get in the way of the flow of oxygen to the brain and may cause you to faint. If you faint once during one of these activities, it's probably not something to worry about. But if it happens more than once, tell your doctor about it.
If you faint when you turn your head to the side, the bones in your neck may be pinching on one of the blood vessels that leads to your brain. If this happens to you, be sure to tell your doctor about it.
A drop in your blood sugar may also cause you to faint. This can happen if you have diabetes, but it may also happen if you don't eat for a long time.
Some prescription medicines can cause fainting. Be sure to talk to your doctor if you think your fainting may be related to a medicine you're taking. Alcohol, cocaine and marijuana can also cause fainting.
More serious causes of fainting include seizures and problems with the heart or with the blood vessels leading to the brain.
People who have certain medical conditions are more likely to faint. These conditions include:
Your doctor will probably ask you about what was happening or what you were doing when you fainted. He or she may ask you for details about how you felt right before and right after you fainted. Your doctor will probably also want to examine you and may perform some tests to find out why you fainted.
Before fainting, you may feel lightheaded, dizzy, like the room is spinning, sick to your stomach. You may also have blurry vision or a hard time hearing. If you feel like you're going to faint, lie down. If you can't lie down, sit and bend forward with your head between your knees. This helps get the blood flowing to your brain. Wait until you feel better before trying to stand up. When you stand up, do so slowly.
You probably don't need to go to your doctor if you have only fainted one time and you are in otherwise good health. Fainting is common and usually not serious. However, if you have serious health problems, especially heart-related problems, high blood pressure or diabetes, you probably should see your doctor. See your doctor if you faint and also have any of these symptoms or conditions:
Written by familydoctor.org editorial staff