What is hematocrit?
Hematocrit is the percentage of red blood cells in your total blood volume, measured as part of routine blood work to check oxygen-carrying capacity.
Hematocrit measures the proportion of red blood cells in your blood as a percentage. A typical test reports this value alongside hemoglobin and white blood cell counts during routine blood work. The normal range for men sits between 41 and 50 percent, though laboratories may vary slightly in their reference ranges.
Red blood cells carry oxygen throughout your body, so hematocrit directly reflects how much oxygen your blood can transport. Higher hematocrit means more oxygen delivery to tissues and organs. When hematocrit climbs too high, your blood becomes thicker and more viscous, which increases the workload on your heart and raises the risk of clotting.
Testosterone replacement therapy increases hematocrit because testosterone stimulates erythropoiesis, the process your bone marrow uses to produce red blood cells. This is one reason why clinics that provide men's health treatment monitor hematocrit levels regularly during TRT. Most practices order blood work at baseline, then at intervals during your first year of treatment, and periodically afterward. If hematocrit rises above safe thresholds (typically 54 percent or higher), your provider may adjust your testosterone dose, space out injections, switch delivery methods, or recommend blood donation to bring levels back down. Routine monitoring helps balance the benefits of testosterone replacement against cardiovascular risk.