WBC count Health Article

Definition

A 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:

• Basophils
• Eosinophils
• Lymphocytes (T cells and B cells)
• Monocytes
• Neutrophils

See also: Blood differential

Alternative Names

Leukocyte count; White blood cell count

How the test is performed

Blood 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 test

No special preparation is usually needed.

How the test will feel

When 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 performed

The 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 Values

4,500-10,000 white blood cells/mcL (cells per microliter)