A WBC count is a blood test to measure the number of white blood cells (WBCs) in the blood.
WBCs help fight infections. They are also called leukocytes. There are five major types of white blood cells:
A blood sample is needed.
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.
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.
You will have this test to find out how many WBCs you have. Your body produces more WBCs for several reasons. The most common reasons are when you have an infection or allergic reaction. You can also have more WBCs when you are under stress or have inflammation. Some people naturally have a "normal" high or low number of WBCs. An increased number of WBCs can be due to a blood cancer, such as leukemia or lymphoma.
The normal number of WBCs in the blood is 4,500 to 11,000 white blood cells per microliter (mcL).
Normal value ranges may vary slightly among different labs. Some labs use different measurements or may test different specimens. Talk to your doctor about your test results.
LOW WHITE BLOOD CELL (WBC) COUNT
A low number of WBCs is called leukopenia. A WBC count below 4500 is below normal
One type of white blood cell is the neutrophil. This type of white blood cell is important for fighting infections.
It may be due to:
HIGH WHITE BLOOD CELL COUNT
A high number of WBCs is called leukocytosis. It may be due to:
There may also be less common reasons for this result.
Drugs that may lower your WBC count include:
Drugs that may increase WBC counts include:
Veins and arteries vary in size from one patient 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:
Reviewed By: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.