Fainting is a sudden, brief loss
of consciousness. When people faint, or pass out, they usually fall down. After
they are lying down, most people will recover quickly.
doctors use for fainting is
syncope (say "SING-kuh-pee").
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:
It happens during exercise or a vigorous activity.
It happens without warning or if it happens when you are already lying down. (When fainting is not serious, a
person often knows it is about to happen and may vomit or feel hot or
You are losing a lot of blood. This could include internal
bleeding that you can't see.
You feel short of breath.
You have chest pain.
You feel like your heart is
racing or beating unevenly (palpitations).
along with numbness or tingling on one side of the face or body.
What exams and tests might you need?
To find the
cause of fainting, a doctor will do a physical exam and ask questions about the
fainting episode. You can help your doctor by being prepared to describe what
happened before you fainted, how long you were "out," and how you felt when you
Depending on what the physical exam shows, the doctor may
want to do tests. These tests may include:
Heart tests such as
ECG, ambulatory monitoring (with a Holter monitor or
event monitor, for example),
echocardiogram, or an exercise stress
A tilt table test. This test checks how your body responds to
changes in position.
Tests for nervous system problems, such as
CT scan of the head,
MRI of the brain, or
What should you do about fainting?
If you know you tend to faint at certain times (such as
when you get a shot or have blood drawn), it may help to:
Sit with your head between your knees or lie
down if you feel faint or have warning signs such as feeling dizzy, weak, warm,
or sick to your stomach.
Drink plenty of fluids so you don't get
How this information was developed to help you make better health decisions.