Overproduction of Red Blood Cells in Dogs

Polycythemia is a term referring to excessive numbers of red blood cells (RBCs, erythrocytes) in the body. It is a rather serious blood condition, characterized by an abnormal increase in the amount of red blood cells in the circulatory system. The condition results in an increase in Packed Cell Volume (PCV), hemoglobin concentration, and in red blood cell count above reference ranges. When this happens, the thickness or viscosity of the blood is increased and causes a multitude of problems.

Polycythemia, also known as erythrocytosis, is classified into three different forms; relative, transient, or absolute. Each form has its own cause and treatment and it is very important that the form is properly diagnosed.

Relative polycythemia is a condition in which the red blood cell numbers are increased due to a large loss of plasma, or water, from the bloodstream, or due to a release of large amounts of red blood cells into the bloodstream. In this condition no extra red blood cells are produced by the dog’s body.

Transient polycythemia is caused by splenic contraction, which injects concentrated RBCs into the circulation in a momentary response to epinephrine, the hormone that reacts to stress, anger, and fear.

Absolute polycythemia is either primary or secondary. Primary absolute polycythemia occurs from a bone marrow disease which causes increased production of red blood cells; at this date it is not yet known why the disease develops. Secondary absolute polycythemia occurs from an increase in erythropoietin, a hormone that regulates red blood cell production; this condition can develop as a result of heart disease or heart failure, or as a result of problems within the kidneys themselves.

Different types of polycythemia produces different type of signs and symptoms in the affected dogs which are listed below




Lack of water intake

Excessive urination


Lack of energy

Low exercise tolerance

Dark-red, or bluish gums



Enlarged abdomen

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