This document discusses the determination of hematocrit (Hct), which is the percentage of red blood cells in blood. Hct is measured by centrifuging a blood sample in a microhematocrit tube to separate the plasma and packed red blood cells. The ratio of the height of the red blood cell layer to the total height provides the Hct percentage. An increased or decreased Hct can indicate various medical conditions like anemia or polycythemia. The normal Hct range is 40-54% for males and 36-47% for females. Proper technique and avoiding sources of error are important for obtaining an accurate Hct measurement.