the hematocrit is composed of
The hematocrit blood test determines the percentage of red blood cells (RBC's) in the blood. Blood is composed mainly of red blood cells and white blood cells 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 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 physician a lot about a person's health.