50% hematocrit is basically ideal for an athlete/lifter that is otherwise healthy. But you can expect it to rise if you add gear, especially things like Test, Nandrolone, Primo, EQ, & Anadrol.
The heavier you get, especially if you are gaining total size or muscle in the neck and chest, the worse sleep apnea gets. As you become hypoxic while sleeping due to the apneas, your body compensates over time by increasing RBC production to carry more oxygen to help offset the lack of total oxygen intake.
If you lose significant weight or get a CPAP or one of those custom fit mouthpieces, the issue can be reversed. As long as the airflow returns to normal at night time.
You should also check your ferritin levels, to see if you actually may just have elevated iron levels. If so, that’s pretty easy to bring down with IP6 or polyphenol supplements or dairy/calcium consumed concurrently with your meals containing any dietary iron.