Hematocrit is a standard component of a complete blood count (CBC) test, expressing the ratio of the volume of red blood cells (RBCs) to the total volume of blood as a percentage. This measurement is essential for evaluating the body's capacity to carry oxygen, thereby assessing overall health and detecting conditions like anemia (low hematocrit) or polycythemia (high hematocrit). In the context of testosterone replacement therapy (TRT), monitoring hematocrit levels is particularly important, as elevated testosterone levels can lead to an increase in RBC production, potentially resulting in a high hematocrit. This condition, known as erythrocytosis, can increase the risk of blood clots, hypertension, and cardiovascular events. Managing hematocrit levels involves addressing the underlying cause, which may include adjusting the dosage of testosterone in TRT patients or employing therapeutic phlebotomy to reduce blood viscosity and improve circulation.