Testosterone Replacement Therapy (TRT) has become an increasingly common treatment for men experiencing low testosterone levels due to aging or hypogonadism. While TRT can significantly improve quality of life by alleviating symptoms such as fatigue, depression, and decreased libido, it is not without potential side effects. One such side effect is polycythemia, a condition characterized by an increased number of red blood cells. This article explores the relationship between TRT and polycythemia, including the mechanisms, risks, and management strategies. What is Polycythemia? Polycythemia is defined by an elevated hematocrit (Hct), hemoglobin (Hb), and red blood cell (RBC) count. Hematocrit refers to the proportion of blood volume occupied by red blood cells. There are two main types of polycythemia: Primary Polycythemia (Polycythemia Vera) : A rare blood disorder where the bone marrow produces too many red blood cells due to a genetic mutation. Secondary Polycythemia : C