Erythrocytosis is often occurring in both transgender people and hypogonadal men treated with testosterone. However, guidelines on how to handle testosterone induced erythrocytosis vary and studies on the cut-off values and management in these groups are scarce. Especially in the transgender population, who are often young and without comorbidity, a phlebotomy seems like an exorbitant measure to reduce red blood cell levels. We present a guideline for the management of testosterone induced erythrocytosis. If hematocrit levels before initiation of testosterone therapy are >0.48 in transgender people or >0.50 in hypogonadal men, without a clear explanation, diagnostics for secondary causes of erythrocytosis should be considered (JAK-mutation, EPO). If levels rise ≥0.52 during testosterone treatment, there should be counseling to prevent a further rise. This can include a dose reduction (if possible), cessation of tobacco use, weight loss if BMI is high (>25), proper treatment for asthma/COPD or if indicated OSAS diagnostics, and switch from injections to gel. Moreover, in the absence of any of these risk factors, diagnostics for secondary causes should be taken into consideration. A hematocrit level of ≥0.56 is considered a reason for phlebotomy from a rheological perspective. When there is a medical history of cardiovascular disease a lower cut-off value for phlebotomy could be applicable (e.g. 0.52) but this is case specific and should be considered on an individual level.