Absolute polycythemia is where the hematocrit is above 55% because of increased RBC count.
Primary means there is no underlying cause whereas secondary means that something else is causing RBC count to increase. And relative polycythemia is where the hematocrit is increased due to lowered plasma volume, not RBC count.
Now I am wondering, my Kepler Bb people live underground so it gets harder to breathe the deeper down you go. 1 common cause of secondary polycythemia is chronic hypoxia.
So would it be good if everyone had the genetics for an increased RBC count? Then this elevated RBC count would be normal for them and they wouldn't have as much trouble breathing in areas of lower oxygen concentration. On the other hand this requires a higher amount of iron to sustain and if polycythemia was normal than our normal would be anemia.
So unless they had lots and lots of iron rich food nearby, it would be easy to get iron deficiency anemia if the normal is polycythemia.
So I am wondering, should my Kepler Bb people naturally have polycythemia as their baseline level of RBCs to increase oxygen transport when they go deep underground but at a risk of easily getting Iron Deficiency Anemia or have normal RBC count but at a greater risk of getting hypoxia?