What is polycythemia from TRT and how dangerous is it?

Testosterone-induced polycythemia (elevated red blood cell mass) occurs in approximately 5–20% of men on TRT, driven by testosterone stimulating erythropoietin production in the kidneys, hematocrit above 54% substantially increases blood viscosity, impairs microvascular flow, and increases risk of deep vein thrombosis, pulmonary embolism, and stroke, making hematocrit monitoring every 3–6 months on TRT a clinical imperative, not an optional measure (Calof et al., J Gerontol A Biol Sci Med Sci, 2005).

The TRAVERSE trial confirmed a 2.3-fold higher PE risk in the TRT group, polycythemia-driven thromboembolism is a real mechanism behind this finding. The clinical management: hematocrit above 50% requires increased monitoring frequency. Hematocrit 50–54%, dose reduction, increased hydration (plasma expansion reduces hematocrit proportionally), switch to lower-androgenicity formulation. Hematocrit above 54%, hold TRT, phlebotomy (venesection), retest in 4–6 weeks. Resume at lower dose.

Honesty Scale: Solid (1) for polycythemia as a real, dose-dependent TRT side effect. Solid (1) for the monitoring and management thresholds.

What to do: At every TRT follow-up visit (every 3 months in the first year), ensure a CBC with hematocrit is ordered and reviewed. Do not accept a TRT follow-up that consists only of a symptom review without a hematocrit result.

For the full picture, read The Testosterone/TRT Deep Dive