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.
common causes of fainting are usually not signs of a more serious illness. In these cases, you faint because
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.
Orthostatic hypotension, or a sudden drop in blood pressure when you change
position. This can happen if you stand up too fast, get
dehydrated, or take certain medicines, such as ones
for high blood pressure.
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: