Test Details: Hematocrit (HCT) is used to measure red blood cell mass. A lower than normal hematocrit can indicate: an insufficient supply of healthy red blood cells (anemia), infection or a white blood cell disorder such as leukemia or lymphoma, vitamin or mineral deficiencies. A higher than normal hematocrit can indicate: dehydration, a disorder such as polycythemia vera that causes increased production of red blood cells, lung or heart disease.