Diseases that cause high white blood cell counts include bacterial infections, anemia, inflammatory diseases and leukemia. The body also produces more white blood cells as a reaction to stress, burns, cigarette smoking and medications. Normal white blood cell counts are between 4,500 and 10,000 cells per microliter, according to MedlinePlus.
When the body's immune system detects threats, it increases the production of white blood cells. The various types of white blood cells kill and digest bacteria, cancer cells and parasites to protect the body. Bone marrow diseases, including leukemia, cause an abnormal production of the white cells, according to the University of Rochester Medical Center. Some white blood cells the body stores in the blood and lymphatic system have a normal lifespan of one to three days. Humans are constantly replacing the cells that die with new ones.
High white blood cell counts are normally discovered when a doctor orders blood work in the diagnosis of symptoms the patient is already experiencing. The high white cell count, along with the results from other tests, is useful in diagnosing the underlying disease causing the patient's symptoms, according to Mayo Clinic.
Some people have a normally elevated high blood cell count. Those without a spleen, due to an earlier surgery, will always have an elevated count, according to MedlinePlus.