Does this test have other names?
HCT, packed cell volume, PCV
What is this test?
This test measures how much of your blood is made up of red blood cells.
Normal blood contains white blood cells, red blood cells, platelets, and the fluid
portion called plasma. The word hematocrit means to separate blood. In this test,
your red blood cells are separated from the rest of your blood so they can be measured.
Your hematocrit (HCT) shows whether you have a normal amount of red blood cells, too
many, or too few. To measure your HCT, your blood sample is spun at a high speed to
separate the red blood cells.
Why do I need this test?
You may need this test if it is part of routine blood testing. You may also need your
HCT checked before having surgery or if your healthcare provider suspects you have
a red blood cell disorder. Too many red blood cells is called polycythemia. Too few
red blood cells is called anemia.
Polycythemia may cause:
Anemia can be caused by blood loss, your body making fewer red blood cells, or increased
destruction of red blood cells. Symptoms may include:
Shortness of breath
Cold, pale skin
What other tests might I have along with this test?
Your healthcare provider may also order a complete blood count (CBC), which is a blood
test that counts all the different types of cells in your blood.
Your healthcare provider may also order a test that measures your hemoglobin to find
out how much oxygen your red blood cells are carrying.
What do my test results mean?
Test results may vary depending on your age, gender, health history, and other things.
Your test results may be different depending on the lab used. They may not mean you
have a problem. Ask your healthcare provider what your test results mean for you.
Results are given as a percentage. Normal HCT values are different for men, women,
and children. Normal values are:
If your HCT is high, it may mean your body is making too many red blood cells. Your
HCT may also be high if your plasma or blood volume is too low. This can happen when
you are dehydrated or in shock.
If your HCT is low, it means you may have:
How is this test done?
The test is done with a blood sample. A needle is used to draw blood from a vein in
your arm or hand.
Does this test pose any risks?
Having a blood test with a needle carries some risks. These include bleeding, infection,
bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may
feel a slight sting or pain. Afterward, the site may be sore.
What might affect my test results?
Living at a high altitude may cause your HCT to be higher than normal. Being pregnant
or being older than age 60 can cause your HCT to be lower than normal.
Certain medicines can also affect your results.
How do I get ready for this test?
You don't need to prepare for this test. Be sure your healthcare provider knows about
all medicines, herbs, vitamins, and supplements you are taking. This includes medicines
that don't need a prescription and any illegal drugs you may use.