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WBC count

Basophil (close-up)
Formed elements of blood

Definition

A WBC count is a blood test to measure the number of white blood cells (WBCs) in the blood.

WBCs are also called leukocytes. They help fight infections. There are five major types of white blood cells:

Alternative Names

Leukocyte count; White blood cell count; White blood cell differential; WBC differential; Infection - WBC count; Cancer - WBC count

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

Most of the time, you do not need to take special steps before this test. Tell your health care provider the medicines you are taking, including the ones without a prescription. Some drugs may change the test results.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.

Why the Test is Performed

You will have this test to find out how many WBCs you have. Your provider may order this test to help diagnose conditions such as:

Normal Results

The normal number of WBCs in the blood is 4,500 to 11,000 WBCs per microliter (4.5 to 11.0 × 109/L).

Normal value ranges may vary slightly among different labs. Some labs use different measurements or may test different specimens. Talk to your provider about your test results.

What Abnormal Results Mean

LOW WBC COUNT

A low number of WBCs is called leukopenia. A count less than 4,500 cells per microliter (4.5 × 109/L) is below normal.

Neutrophils are one type of WBC. They are important for fighting infections.

A lower than normal WBC count may be due to:

HIGH WBC COUNT

A higher than normal WBC count is called leukocytosis. It may be due to:

There may also be less common reasons for abnormal WBC counts.

Drugs that may lower your WBC count include:

Drugs that may increase WBC counts include:

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

References

Chernecky CC, Berger BJ. Differential leukocyte count (Diff) - peripheral blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:441-450.

Vajpayee N, Graham SS, Bem S. Basic examination of blood and bone marrow. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 30.


Review Date: 1/29/2019
Reviewed By: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.