White Cell Count
Does this test have other names?
What is this test?
This test measures the number of white blood cells (WBCs) in your blood. Cells in
your bone marrow make white blood cells and release them into the bloodstream. White
blood cells help you fight infection. They are part of your body's immune system,
which keeps you healthy and makes you well when you get sick. White blood cells work
to destroy any foreign virus, fungus, or bacteria that enter your body.
When you get sick, your white blood cell count is higher than normal. This is because
your body is releasing more of these cells to fight the infection. But if you have
certain illnesses like HIV or cancer, your white blood cell count can drop to very
low levels. It can also drop if you are on medicine that weakens your immune system.
This includes medicines such as chemotherapy.
White blood cells are divided into 5 main types:
This test measures the total count of all types of white blood cells. It does not
measure the levels of each type of white blood cells.
Why do I need this test?
You may need this test to find out if you have an infection or illness. If your immune
system is weakened by medicine or illness, you may also need this test to see if your
white blood cell count is too low. If it is, even a simple infection could be very
harmful to your body.
What other tests might I have along with this test?
You may also have these tests:
Differential white blood cell count. This blood test measures the amount of each type of white blood cells.
Complete blood count (CBC). This measures all of the major blood cells, including white blood cells.
Neutrophil test. This may be done to check for neutropenia. If you have neutropenia, it means your
neutrophil count is low and you can easily get an infection.
Bacterial and viral cultures. Your healthcare provider may also send samples of your blood, urine, sputum, and
cerebral spinal fluid (CSF) to the lab to check for bacteria and viruses.
Imaging tests. You may have imaging tests, such as an MRI or CT scan, to look for sources of infection.
Biopsy. If your healthcare provider thinks you may have a type of blood cancer, you may need
a biopsy to help figure out the cause of your abnormal WBC values.
What do my test results mean?
Test results may vary depending on your age, gender, health history, the method used
for the test, and other things. Your test results may not mean you have a problem.
Ask your healthcare provider what your test results mean for you.
Normal white blood cell counts are:
9,000 to 30,000/mm3 for newborns
6,200 to 17,000/mm3 for children under 2 years old
5,000 to 10,000/mm3 for children older than age 2 up to adults
Test results that are higher than normal may mean that you have an infection or illness
that your body is fighting. Test results that are lower than normal may mean that
your immune system isn't working as well as it should. This means that even a small
infection could cause serious health problems.
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. Infants usually have one of their heels stuck with a needle to collect
a few drops of blood.
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?
Some medicines may affect your test results. Tell your healthcare provider about treatments
you are getting, medicines you are taking, or recent illnesses you've had.
How do I get ready for this test?
You can probably eat, drink, and take your medicine as usual, but check with your
healthcare provider. Be sure your 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.