What is polycythemia?

Erythrocytosis refers to a condition in which the number of red blood cells per unit volume of blood exceeds the upper limit of the normal range. Specifically: 1. Definition: Erythrocytosis is a state in which the number of red blood cells in the blood surpasses the normal range. 2. Reference values: In adults, erythrocytosis is defined as more than 6 million red blood cells per cubic millimeter (6.0×10¹²/L) and hemoglobin levels exceeding 170 g/L for males, or more than 5.5 million red blood cells per cubic millimeter (5.5×10¹²/L) and hemoglobin levels exceeding 160 g/L for females. 3. Causes: Erythrocytosis may be caused by various factors, including physiological conditions (e.g., newborns, individuals residing at high altitudes) and pathological conditions (e.g., polycythemia vera, secondary erythrocytosis). Erythrocytosis can affect multiple systems and lead to a range of symptoms. Treatment should be based on the underlying cause.