White blood cell count (WBC)
Total number of white blood cells, a core value of every blood count
Also known as
Definition
White blood cells (leukocytes) are an important part of the body's defenses. The test measures their total number per volume of blood. There are five main types: neutrophils, lymphocytes, monocytes, eosinophils and basophils, whose shares are broken down in the blood differential. The white blood cell count shows whether there are too many or too few white blood cells, but on its own it does not confirm a diagnosis.
| Parameter | Value |
|---|---|
| Unit | /nl (= 10⁹/l) |
| Reference Range | Typical for adults: 4.5–10.0 /nl (4,500–10,000 /µl). Factors such as age or altitude can affect the normal range, and labs differ slightly; the reference range on your own report is what counts. Discuss any deviation with your doctor. |
Agree on your personal target range with your doctor.
1 /nl equals 1 × 10⁹/l and 1,000 /µl; some labs write G/l or thousand/µl. US reports use cells/mcL (4,500–10,000).
↓ What a low value means
A low white blood cell count (leukopenia, below about 4,500 /µl) can be linked to bone marrow damage, for example from infection, disease or chemotherapy, cancers that affect the bone marrow, lymphoma, autoimmune diseases such as lupus, HIV, or liver or spleen disease. Certain medicines, such as some antibiotics, can also lower the count. The value alone is not a diagnosis; discuss it with your doctor.
↑ What a high value means
A high white blood cell count (leukocytosis) can be linked to bacterial or viral infections, inflammatory diseases such as rheumatoid arthritis, autoimmune diseases, allergies, tissue damage for example after burns or surgery, leukemia or Hodgkin lymphoma. Smoking, stress, pregnancy or a reaction to a medicine, such as certain steroids, can also raise the count. A high value alone does not confirm a diagnosis; a blood differential often follows. Discuss the result with your doctor.
When to test
The white blood cell count is part of every blood count, for example during routine checkups, with signs of infection or inflammation such as fever, chills, body aches or a persistent cough, and for monitoring conditions or medicines that weaken the immune system. No special preparation is needed. Tell your doctor about your medicines, but do not stop any on your own.
Frequently asked questions
What is the difference between the white blood cell count and the blood differential? +
The white blood cell count gives the total amount of white blood cells. The blood differential shows how this total is split among neutrophils, lymphocytes, monocytes, eosinophils and basophils. If the total is unusual, the differential is often added.
Can medicines change the white blood cell count? +
Yes. Chemotherapy and certain other medicines, such as some antibiotics, can lower the count; certain steroids can raise it. Mention your medicines before the blood draw and do not stop any without talking to your doctor.
Do I need to fast for a white blood cell count? +
No, no special preparation is needed. The sample is taken from a vein in your arm like any other blood draw.
Can smoking or stress affect the white blood cell count? +
Yes. Smoking and stress are among the possible reasons for a high white blood cell count. Alcohol or a physical injury can also affect white blood cell results. Doctors therefore always interpret the value together with symptoms, medical history and the other blood results.
White blood cell count (WBC)
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.