MedlinePlus states that a normal hematocrit level typically ranges from 40.7 to 50.3 percent in men and 36.1 to 44.3 percent in women. In children, a normal hematocrit ranges from 45 to 61 percent in newborns and 32 to 42 percent in infants.
Wikipedia explains that the hematocrit is the percentage of whole blood that is made up of red blood cells, and it depends on the number and size of red blood cells. It is often included in a complete blood count test. A low hematocrit could be due to anemia, blood loss, malnutrition or overhydration, while a high hematocrit could be caused by congenital heart disease, low blood oxygen levels or dehydration.