Testing to determine a white blood cell count is recommended when there are symptoms of infection or inflammation, according to Lab Tests Online. Testing should also be requested when symptoms indicate the possibility of a blood disorder, autoimmune disorder or an immune deficiency.
WBCs, also known as leukocytes or immune cells, help defend the body against infectious disease and foreign materials and are part of the immune system, according to ScienceDaily. Although WBCs account for only 1 percent of blood, they are critical for good health and protection against illness and disease, notes the University of Rochester Medical Center.
Although the threshold for low WBC levels varies depending on age and sex, a count lower than 4,000 WBCs per microliter of blood is typically considered a low count, explains Mayo Clinic. A low WBC count may result from medical conditions such as an autoimmune disorder that destroys WCBs, bone marrow problems, cancer or certain medications. A high WBC count may indicate the presence of infection, inflammation, an immune system disorder, bone marrow disease or a reaction to medication.
Other factors that may result in high WBC levels include extreme physical or emotional stress, labor during childbirth, the end of pregnancy, smoking or extreme exercise, according to the University of Rochester Medical Center.