Quantity: * Whole number only. A complete blood count (CBC) is a laboratory test that measures several basic parameters of human blood including the red blood cell counts (erythrocytes), white blood cell counts (leukocytes) and platelets (thrombocytes).A CBC with differential is often ordered to determine a patients general health status. complete blood count (CBC) is a laboratory test that measures several basic parameters of human blood including the red blood cell counts (erythrocytes), white blood cell counts (leukocytes) and platelets (thrombocytes).