Polycythemia is an increase in the number of red blood cells in the bloodstream. Polycythemia rubra vera is a disease in which the blood-producing cells in the bone marrow develop and reproduce abnormally. It has been reported in cats. Red blood cell production is dramatically increased, and levels of the hormone that stimulates development of red blood cells (erythropoietin) are low or normal. In secondary polycythemia, red blood cell production increases in response to increased erythropoietin levels. This may be seen in severe lung disease, congestive heart failure, or abnormalities of blood circulation.

Your veterinarian will use tests of blood and urine to help diagnose polycythemia. In some cases, X-rays and other tests may also be required. Signs of the disorder include red mucous membranes, bleeding tendencies, the passing of large amounts of urine, excessive thirst, seizures or behavioral changes, lack of coordination, weakness, and blindness. Treatment of polycythemia includes removing red blood cells by withdrawing blood through a catheter placed in a vein, then replacing the lost blood with fluids. Drugs such as hydroxyurea or clorambucil may also be added to the treatment. In some cases, the underlying disease must be treated (see Blood Disorders of Dogs: Polycythemia in Dogs).

Last full review/revision July 2011 by Peter H. Holmes, BVMS, PhD, Dr HC, FRCVS, FRSE, OBE; David J. Waltisbuhl, BASc, MSc; Michael Bernstein, DVM, DACVIM; Karen L. Campbell, MS, DVM, DACVIM, DACVD; Nemi C. Jain, MVSc, PhD; Wayne K. Jorgensen, BSc, PhD; Sarah E. Payne, DVM, DACVIM