White Blood Cell Count (WBC) Test
Why am I having this test?
A white blood cell count is done to learn about your white blood cells (leukocytes), which are cells in the blood that help the body fight infection. They are part of the body’s defense system (immune system). When the immune system needs more white blood cells, the tissue inside your bones (bone marrow) makes more and releases them into your blood. They travel through your bloodstream to areas of the body where they are needed.
This test may be done as part of a routine checkup that includes a complete blood count to measure all the cells in your blood. You may also have this test if you have any signs or symptoms of:
- Illness.
- Infection.
- An allergic reaction.
- Inflammation, which is swelling and irritation anywhere in your body. Your white blood cells play a major role in the process of inflammation.
What is being tested?
This test measures how many white blood cells you have. Different types of white blood cells make up your total count. These include:
- Neutrophils.
- Lymphocytes.
- Monocytes.
- Eosinophils.
- Basophils.
Your white blood cell count includes a breakdown of how many of each of these cells you have.
What kind of sample is taken?
A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel.
Tell a health care provider about:
- All medicines you are taking, including vitamins, herbs, eye drops, creams, and over-the-counter medicines.
- Any medical conditions you have.
- Whether you are pregnant or may be pregnant.
- If you have had your spleen removed.
- Any recent physical or emotional stress.
How are the results reported?
Your test results will be reported as numbers for each type of white blood cell and a total count of all the white blood cells in your sample. These will be given as a number of cells per cubic millimeter (mm3) of blood. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:
Total white blood cells:
- Adults and children over 2 years of age: 5,000–10,000/mm3.
- Children age 2 years or younger: 6,200–17,000/mm3.
- Newborn: 9,000–30,000/mm3.
Total for each type of white blood cell:
- Neutrophils: 2,500–8,000/mm3.
- Lymphocytes: 1,000–4,000/mm3.
- Monocytes: 100–700/mm3.
- Eosinophils: 50–500/mm3.
- Basophils: 25–100/mm3.
What do the results mean?
Results lower than the reference ranges mean that you have a low white blood cell count (leukopenia). Common causes include:
- Severe bacterial infections.
- Some viral infections.
- Some immune system diseases.
- Some medicines.
- Some bone marrow diseases.
- Cancer or cancer treatments.
Results higher than the reference ranges mean that you have a high white blood cell count (leukocytosis). Common causes include:
- Bacterial and other infections.
- Injury (trauma).
- Allergic reactions.
- Diseases that cause inflammation.
- Stress.
- Some medicines.
- White blood cell cancers.
Talk with your health care provider about what your results mean.
Questions to ask your health care provider
Ask your health care provider, or the department that is doing the test:
- When will my results be ready?
- How will I get my results?
- What are my treatment options?
- What other tests do I need?
- What are my next steps?
Summary
- A white blood cell count is done to learn about your white blood cells (leukocytes), which are the immune system cells in your blood that help you fight infection.
- This test may be done as part of a routine checkup. A white blood cell count may also be done if you have signs or symptoms of infection or other illness.
- A low white blood cell count is called leukopenia. A high white blood cell count is called leukocytosis.
