The Full form of HCT is Hematocrit. HCT is the proportion of the blood that consists of packed red blood cells. The Hematocrit is expressed as a percentage by volume and the red cells are packed by centrifugation. For example, an HCT of 25% means that there are 25 milliliters of red blood cells in 100 milliliters of blood. The red cells make up a quarter of the blood. The HCT blood test determines the percentage of RBC’s (Red Blood Cells) in the blood. Blood is composed mainly of red blood cells and white blood cells (WBC’s) suspended in an almost clear fluid called serum. The hematocrit test indicates the percentage of blood by volume that is composed of red blood cells. The condition and a disease called “Anemia” results from having too few red blood cells. Anemia causes a variety of symptoms. The hematocrit is a basic test that can tell a doctor a lot about a person’s health. A low HCT means the percentage of red blood cells is below the lower limits of normal for that person’s age, sex, or specific condition (for example, pregnancy or high-altitude living). Another term for low hematocrit is anemia.