Hematocrit is a medical term that refers to the proportion of blood volume that is made up of red blood cells. It is usually expressed as a percentage. A higher hematocrit level indicates a greater concentration of red blood cells, which can affect the blood's ability to carry oxygen. Doctors often measure hematocrit during routine blood tests to assess a person's overall health. Normal hematocrit levels vary by age and sex, but abnormal levels can indicate conditions such as anemia or dehydration. Monitoring hematocrit helps in diagnosing and managing various health issues.