It's a blood disorder in which the bone marrow makes too many red blood cells. Polycythemia vera may also result in the overproduction of white blood cells and platelets. Most of the health concerns associated with polycythemia vera are caused by a blood-thickening effect that results from an overproduction of red blood cells.
Bloodletting is one form of treatment, which often may be combined with other therapies. The removal of blood from the body reduces the blood volume and brings down the hematocrit levels; in patients with polycythemia vera, this reduces the risk of blood clots.
Low dose aspirin (75–81 mg daily) is often prescribed. Research has shown that aspirin reduces the risk for various thrombotic complications.