Blood transfusions can actually save the life of an animal. However, the risk of possible reactions must be taken into account, requiring intensive monitoring in the first 30 minutes of transfusion, during which the transfusion speed must be slow. Thus, the risk can be reduced and reactions identified early. The percentage of adverse reactions in dogs and cats is aproximately 2.5% and 2%, respectively.

The transfusion reactions can be classified as immune-mediated (due to the interaction Ab -Ag) or non-immune-mediated (due, for example, to contamination, improper handling or cytokine activation in the blood to be transfused); the latter are independent of the immune status of the recipient and do not require prior sensitization. The reactions can also be classified as acute (during transfusion and up to a few hours after) or delayed (after days or weeks). The following tables summarize the various types of reactions, their treatment and prevention methods.