A WBC level, also referred to as a white blood cell count, is the measure of white blood cells in the blood. White blood cells fight infection and respond to the presence of foreign substances like allergens. Examples of white blood cells are neutrophils, lymphocytes, monocytes, eosinophils and basophils. A total white blood cell count measures the total number of white blood cells in the body, and a differential count measures each type of white blood cell.
Neutrophils kill and digest bacteria in the body. Monocytes also fight bacteria, but generate faster and last longer than neutrophils. Basophils and eosinophils respond to allergic reactions and parasitic infestations. Lymphocytes fight long-lasting bacterial infections and sudden onset viral infections.
Fasting is not required before a white blood cell count. A health care professional will obtain a blood sample from a vein in your arm or hand and send the sample to a laboratory for processing. Side effects of having your blood drawn include mild to moderate pain and a throbbing sensation at the injection site.
According to MedlinePlus.com, a normal white blood cell count is between 4,500 to 10,000 white blood cells per microliter. Normal levels of the different types of white blood cells in a differential count are 40 percent to 60 percent neutrophils, 20 percent to 40 percent lymphocytes, 2 percent to 8 percent monocytes, 1 percent to 4 percent eosinophils and 0.5 percent to 1 percent basophils. Since some laboratories have slight variations related to normal lab values, your physician will determine if your white blood cell level is abnormal.
Certain medications may cause abnormal white blood cell level results. Medications that can cause an increased number of white blood cells include triamterene (Dyrenium), steroids, quinine, heparin, epinephrine, chloroform, aspirin, allopurinol and adrenaline. Factors that may increase white blood cell values include the final month of pregnancy, labor, physical activity and surgical removal of the spleen. Medications that may cause a decreased level of white blood cells include sulfonamides, diuretics, antihistamines, chemotherapeutic agents, barbiturates, arsenicals, anticonvulsants and antibiotics.
An increased level of white blood cells, also referred to as leukocytosis, may indicate inflammation due to allergies or rheumatoid arthritis, tissue damage, severe emotional or physical stress, trauma, anemia, leukemia, neoplasia and infection. A decreased level of white blood cells, also referred to as leukopenia, may indicate congenital marrow hyperplasia, bone marrow infiltration, dietary deficiency, overwhelming infections, radiation therapy, lupus erythematosus, disease of the spleen or liver, bone marrow failure and drug toxicity from chloramphenicol.