High Red Blood Cell Count (Erythrocytosis) - What do I need to know?

Greetings. A question for the internists or anyone with medical insight. Over the last year or two, I've noticed my red blood cell count creeping up. My latest labs showed an RBC of 6.24 million and a hematocrit of 0.525. I went through a full workup with a hematologist and everything else came back normal; erythropoietin was 16 (range 4-33). JAK2 mutation was negative. White cells and platelets are fine, so we're looking at isolated erythrocytosis. I don't smoke, and I certainly don't live in the Rockies. Interestingly, my MCV is at the lower limit (84.2) while my MCH is slightly low (26.8).

I'm feeling a bit lost here. Any thoughts on what the next step might be?