What is HCT in a blood test?

HCT in a blood test is hematocrit, the percentage of the blood made up of red blood cells, says MedlinePlus. Normal hematocrit results are 40.7 to 50.3 percent for males and 36.1 to 44.3 percent in females. Newborns have slightly higher levels than adults, and infants have slightly lower levels.

Potential causes for low hematocrit include anemia, leukemia, overhydration, malnourishment, bleeding, destruction of red blood cells, and not having enough iron, folate, vitamin B-12 and vitamin B-6, explains MedlinePlus. High hematocrit levels may be the result of congenital heart disease, scarring of the lungs, dehydration, bone marrow disease and low blood oxygen levels.