Hematocrit is a measure of the percentage of red blood cells (RBCs) in a given volume of blood. Hematocrit systems measure this laboratory value as an indicator of patient well being, as one measure of the adequacy of patient blood component production and to screen for conditions such as occult blood loss. Hematocrit systems are used in physician offices, clinics and hospitals to evaluate patient condition and to assess the efficacy of treatment regimens.