polycythemia

Polycythemia (also known as polycythaemia or polyglobulia) is a disease state in which the hematocrit (the volume percentage of red blood cells in the blood) and/or hemoglobin concentration are elevated in peripheral blood.

It can be due to an increase in the number of red blood cells ('absolute polycythemia') or to a decrease in the volume of plasma ('relative polycythemia'). Polycythemia is sometimes called erythrocytosis, but the terms are not synonymous, because polycythemia refers to any increase ...