White blood cell count, also known as leukocyte count, refers to the number of white blood cells present in the bloodstream. This measurement is typically included in a comprehensive blood test. White blood cells, crucial for combating infections, differ from red blood cells, which are responsible for transporting oxygen and are called erythrocytes. Various types of white blood cells exist, such as neutrophils (also known as polymorphonuclear cells or PMNs), band cells (which are immature neutrophils), T lymphocytes (T cells), B lymphocytes (B cells), monocytes, eosinophils, and basophils. The complete blood count reflects all these white blood cell types. The standard range for white blood cell count varies across laboratories but generally falls between 4,300 and 10,800 cells per cubic millimeter of blood. This range can also be presented in international units as 4.3 - 10.8 x 10^9 cells per liter. A decreased white blood cell count is referred to as leukopenia, while an increased count is known as leukocytosis.

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