Blood Transfusion Reactions in Cats

There are a variety of reactions that can occur with the transfusion of any blood product. Purebred cats, especially those that have had previous blood transfusions, are at a higher risk for having severe reactions to transfusion than other animals. Most reactions usually occur during, or shortly after, the transfusion.

Symptoms and Types

Reaction to a blood transfusion may be classified by one of the following conditions: immune system related; acute reaction (an immediate, sudden reaction); or delayed reaction.

Acute symptoms of a reaction to blood transfusion may include fever, vomiting, weakness, incontinence, shock, collapse, and general loss of transfusion effectiveness. Symptoms of a delayed reaction are usually not directly apparent and result only in a loss of the transfusion’s effectiveness.

Many symptoms will vary, depending on the exact cause. Transfusion of contaminated blood can result in fever, shock, and septicemia -- an invasion of disease producing bacteria into the bloodstream. Circulatory overload resulting from rapid or excessive transfusion can result in vomiting, cough, and heart failure. Hypothermia, which can stem from transfusion of cold refrigerated blood -- usually in smaller cats or already hypothermic cats -- is evident by shivering and impaired platelet function.


There are several circumstances that may be responsible for a blood transfusion reaction, such as transfusion of a mismatched blood type; transfusion of contaminated blood and consequent blood-born disease from an infected donor; circulatory overload caused by too-rapid or too-large amounts of transfusion; or transfusion of damaged red blood cells which have been improperly stored (i.e., due to excessive heating or freezing). In addition to these causes, the cat’s immune system may react to various components in the donor’s blood. Symptoms will usually surface in the course of 3-14 days.


A diagnosis of blood transfusion reaction is based largely on symptoms that present after transfusion. Tests include a urine analysis, retesting of blood type to confirm rejection of donor blood, and a bacteria analysis of the transfused blood.

Symptoms of reaction that result in fever or hypotension (low blood pressure ) may also be diagnosed as inflammatory disease, or may be found to have been caused by an infectious disease.

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