EPO and Sleep apnea: Acquired erythrocytosis is most frequently a compensatory mechanism in response to a hypoxic condition such as cardiopulmonary disease, hypoventilation (sleep apnea, snoring...), living at high altitudes, tobacco use, but can also be a result of certain medications (diuretics, sodium-glucose cotransporter 2 inhibitors, anabolic steroids) or supplements (androgens), and erythropoietin (Epo).