hematocrit

hematocrit The proportion of the blood that consists of red blood cells. Abbreviated Hct. Hct is expressed as a percentage. For example, an Hct of 25 percent means that there are 25 milliliters of red blood cells in 100 milliliters of blood. The normal ranges for Hct depend on the age and, after adolescence, the sex of the patient. The normal ranges are 40.7 to 50.3 percent in adult males, and 36.1 to 44.3 percent in adult females. The values returned on Hct tests may vary slightly between laboratories. An abnormally low level of Hct is referred to as anemia and can come from bleeding, iron deficiency, breakage of red blood cells (hemolysis), and many other causes. An abnormally high level of Hct is referred to as polycythemia and can be a result of chronic lung disease, polycythemia rubra vera, and other causes. See also CBC.