Certain medical conditions, such as cancer or a serious infection, could affect the normal range of white blood cells during a complete blood count, according to Mayo Clinic. Cancer is likely to cause a decrease in white blood cells, and infection or inflammation could cause an increase.
Other diseases that could cause a person's white blood cell count to be lower include HIV and other types of autoimmune diseases, lupus, and liver or spleen diseases, according to Healthline. Patients undergoing chemotherapy are also prone to developing a low white blood cell count.
Conditions such as tumors in an individual's bone marrow, anemia, asthma, allergies, and other types of inflammatory diseases could cause an individual's white blood cell count to be higher than normal, states Healthline. Pregnancy, stress and exercise can also increase an individual's white blood cell count.
Doctors often check an individual's blood cell count in order to diagnose a specific condition, monitor a specific condition or treatment, and review a patient's overall health, states Mayo Clinic. White blood cells are just one part of a person's blood that is counted, along with red blood cells and platelets. In people who are otherwise healthy, slight variances in normal measurements don't raise much concern. However, major variances could be a sign of disease.