Definition of polycythemia in US English:


(British polycythaemia)


  • An abnormally increased concentration of hemoglobin in the blood, through either reduction of plasma volume or increase in red cell numbers. It may be a primary disease of unknown cause, or a secondary condition linked to respiratory or circulatory disorder or cancer.

    • ‘Severe polycythaemia increases the viscosity of the blood and probably leads to problems with unloading oxygen from the blood to the tissues.’
    • ‘This is more than twice the production rate in adults, primarily because of relative polycythemia and increased red blood cell turnover in neonates.’
    • ‘The differential diagnoses included chronic hepatitis, idiopathic urticaria, uremia, polycythemia, thyroid disease, and malignancy, among others.’
    • ‘Because in chronic pulmonary disease both hypoxemia and polycythemia are simultaneously present, their individual effects on the pulmonary circulation have been difficult to define.’
    • ‘In patients with chronic hypoxemic lung disease, polycythemia has been shown to impair the vasodilator response to acetylcholine.’


Mid 19th century: modern Latin, from poly- ‘many’ + -cyte ‘cell’ + hemo- ‘blood’ + -ia.