What it is:
White blood cells play a role in reducing inflammation in the body. A high white blood cell count could mean that there is inflammation somewhere in the body, such as can occur in the gastrointestinal tract of people who have inflammatory bowel disease (IBD). The white blood cell (WBC) count is also sometimes known as a leukocyte count or white count. A WBC count is typically done along with another common blood test, the complete blood cell count (CBC). A WBC count is the number of white blood cells per volume of blood, and is reported in either thousands in a microliter or millions in a liter of blood.
What it's used for:
A high WBC count can be an indicator of an infection, inflammation, or allergy. Some conditions may cause a decrease in the WBC count.
Leukocytosis is the presence of an elevated WBC count; leukopenia is a decreased WBC count. Leukocytosis may be caused by several conditions including bacterial infection, inflammation, leukemia, trauma, or stress. Leukopenia may occur as a result of chemotherapy, radiation therapy, or immune system disorders.
How it's done:
A blood sample will be taken, normally from the arm. If several tests are ordered, more than one vial of blood will be taken.
The normal range for WBC count is 4,300 to 10,800 cells per cubic millimeter (cmm) or 4.3 to 10.8 x 109 cells per liter. A range of 11 to 17 x 109/L may be considered mild to moderate leukocytosis, and a range of 3.0 to 5.0x109/L may be considered mild leukopenia.