white blood cells are produced in the bone marrow. as they mature white blood cells are continually released into the bloodstream. white blood cells circulate throughout the body ready to fight infections. they live about two or three weeks when they are broken down and recycled by the body. a normal white blood cell count is between about 4 500 and 10 000 cells per microliter. many conditions can cause a low white blood cell count: • infection (which usually increases the white blood cell count but may decrease it). • drugs especially chemotherapy. • human immunodeficiency virus (hiv). • severe alcohol abuse. • radiation therapy. • cancer affecting the bone marrow. • connective tissue disease (such as systemic lupus erythematosus). many african-americans have a naturally lower white blood cell count. this is caused by a gene mutation that may have evolved as a defense against malaria. most often a low white blood cell count is temporary and improves on its own.
what causes a low white blood cell count?