Dr. MJ Bazos MD, Patient Handout
Fainting: What Causes It
What causes fainting?
Fainting, which is also called syncope, can be related to many different things. More than one thing may be the cause of fainting. Sometimes a specific cause for fainting can't be found.
Fainting can happen when not enough oxygen flows through your blood and into your brain. You lose consciousness, or "pass out," for a very brief time -- just a few seconds or minutes.
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. It can happen when:
Coughing, urinating and stretching can also get in the way of the flow of oxygen to the brain and may be a cause of fainting. If you faint once during one of these activities, it's probably not something to worry about. But if it happens more than once, you should 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.
How will the cause of my fainting be found?
Your doctor will probably want to talk to you about exactly what was happening 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.
What should I do if I think I'm going to faint?
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, to help get the blood flowing to your brain. Wait until you feel better before trying to stand up.
Should I see my doctor if I faint?
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 your fainting is associated with any of these features: