ERYTHROCYTOSIS - An abnormal elevation in the number of red blood cells. Normal RBC counts should be in the range of 4.6-6.2 million per cubic millimeter for males and 4.2-5.4 million per cubic millimeter for females. Erythrocytosis may occur for physiologic reasons (to increase oxygen carrying capacity) in those with chronic obstructive pulmonary disease or those who live at higher altitudes.