The hematocrit (Ht or HCT, from the Greek "αιματοκρίτης" which means blood judge'), also known as packed cell volume (PCV) or erythrocyte volume fraction (EVF), is the volume percentage (%) of red blood cells in blood. It is normally 45 or men and 40 or women. It is considered an integral part of a person's complete blood count results, along with hemoglobin concentration, white blood cell count, and platelet count. Because the purpose of red blood cells is to transfer oxygen from the lungs to body tissues, a blood sample's hematocrit—the red blood cell volume percentage—can become a point of reference of its capability of delivering oxygen. Additionally, the measure of a subject's blood sample's hematocrit levels may expose possible diseases in the subject. Anemia refers to an abnormally low hematocrit, as opposed to polycythemia, which refers to an abnormally high hematocrit. For a condition such as anemia that goes unnoticed, one way it can be diagnosed is by measuring the hematocrit levels in the blood. Both are potentially life-threatening disorders.