Fainting one time is usually nothing to worry about. But it is a good idea to see your doctor, because fainting could have a serious cause.
What causes fainting?
Fainting is caused by a drop in blood flow to the brain. After you lose consciousness and fall or lie down, more blood can flow to your brain so you wake up again.
The most common causes of fainting are usually not signs of a more serious illness. In these cases, you faint because of:
The vasovagal reflex, which causes the heart rate to slow and the blood vessels to widen, or dilate. As a result, blood pools in the lower body and less blood goes to the brain. This reflex can be triggered by many things, including stress, pain, fear, coughing, holding your breath, and urinating.
Fainting caused by the vasovagal reflex is often easy to predict. It happens to some people every time they have to get a shot or they see blood. Some people know they are going to faint because they have symptoms beforehand, such as feeling weak, nauseated, hot, or dizzy. After they wake up, they may feel confused, dizzy, or ill for a while.
Some causes of fainting can be serious. These include: