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WBC countDefinitionA WBC count is a blood test to measure the number of white blood cells (WBCs). White blood cells help fight infections. They are also called leukocytes. There are five major types of white blood cells:
See also: Blood differential Alternative NamesLeukocyte count; White blood cell countHow the Test is PerformedBlood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore blood flow. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding. For an infant or young child: The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding. A WBC count is almost always done as part of a CBC (complete blood count). How to Prepare for the TestNo special preparation is usually needed. How the Test Will FeelWhen the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. Why the Test is PerformedThe test is performed to find out how many white blood cells you have. Your body produces more white blood cells when you have an infection or allergic reaction -- even when you are under general stress. Normal Results4,500-10,000 white blood cells/mcL (cells per microliter) What Abnormal Results MeanA low number of WBCs is called leukopenia. It may be due to:
A high number of WBCs is called leukocytosis. It may be due to:
These lists are not all inclusive. RisksA simple blood test is generally safe. In general, risks may 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. ConsiderationsPeople who have had their spleen removed (splenectomy) will always have a slightly higher number of WBCs. Drugs that may increase WBC counts include:
Drugs that may lower your WBC count include:
ReferencesMcPherson RA and Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: WB Saunders; 2007:461-2. Hoffman R, Benz Jr. EJ, Shattil SJ, et al., eds. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, Pa: Churchill Livingston; 2005:2676-77, 2733.
Review Date:
3/8/2007 Reviewed By: Mark Levin, MD, Hematologist and Oncologist, Newark, NJ. Review provided by VeriMed Healthcare Network. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997-
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