Testosterone acts directly on the bone marrow and enhances erythropoietin production in the kidneys, which stimulates the creation of red blood cells (erythropoiesis).
Hematocrit measures the percentage of whole blood made up of red blood cells. When hematocrit exceeds normal ranges (typically above 50% to 54%), blood viscosity increases, which may place additional strain on the cardiovascular system.
Regular monitoring of a complete blood count (CBC) allows the physician to identify erythrocytosis early and adjust medication dosage, alter delivery methods, address underlying sleep apnea, or recommend therapeutic phlebotomy when indicated.
Risks and limitations
- Erythrocytosis is one of the most common dose-dependent laboratory changes associated with testosterone therapy, particularly with injectable formulations.
- Failure to monitor hematocrit regularly can result in unmanaged polycythemia, requiring temporary cessation of therapy.