A 35-year-old man is examined in an urgent care clinic. His presenting symptoms suggest polycythemia vera. Which extreme laboratory value would confirm this possible diagnosis?

A. High iron level: Iron levels do not define polycythemia; in fact, iron may be low because it is being used up to make so many red cells. B. High hemoglobin level: Polycythemia vera is a bone marrow disorder characterized by the overproduction of red blood cells, resulting in abnormally high hemoglobin and hematocrit levels. C. Low platelet count: Polycythemia vera often involves an increase in all marrow-produced cells, including platelets (thrombocytosis), not a decrease. D. Low white cell count: Similar to platelets, white cell counts are often elevated in this condition, not low.