Do pets need blood transfusions too — what happens if blood types don't match?

ImmunityQ&AMeongsiljang Veterinary Advisory Board

Blood transfusions for pets are necessary in life-threatening situations such as anemia, bleeding, or poisoning. We’ve outlined the blood types of dogs and cats, cross-matching procedures, the transfusion process, and important precautions.

What is a pet blood transfusion?

A veterinarian preparing a blood transfusion for a puppy.

Blood transfusions for pets are an emergency treatment that involves administering blood from a healthy donor animal to a recipient whose life is threatened by conditions such as anemia, hemorrhage, or coagulopathy. Crucial steps that must not be overlooked are blood typing and cross-matching. Dogs lack natural antibodies, making their first transfusion relatively safe; while blood typing is not strictly mandatory for the initial transfusion, DEA 1-negative blood is preferred. If a dog receives DEA 1-incompatible blood, a delayed hemolytic reaction may occur within several days, and cross-matching is absolutely required for any subsequent transfusions. Cats, on the other hand, possess natural antibodies from birth, so blood typing is essential even for their first transfusion. In particular, transfusing type A blood into a type B cat can trigger a fatal hemolytic reaction within minutes. Transfusions are typically administered slowly over 2 to 4 hours, with vital signs continuously monitored throughout the procedure.

Situations requiring blood transfusion

Blood transfusions are life-saving treatments, but they are not administered indiscriminately. In dogs, transfusions are typically considered when the packed cell volume (PCV) drops below 20% or when hemodynamic instability occurs due to acute hemorrhage. For cats, the decision to transfuse is based on a comprehensive assessment of the degree of anemia and clinical signs, with the overall clinical condition being more important than any single numerical value. Common indications include traumatic hemorrhage, hemolysis caused by onion or garlic toxicity, immune-mediated hemolytic anemia (IMHA), anemia associated with chronic kidney disease, excessive blood loss during surgery, and spontaneous bleeding due to thrombocytopenia. As stated in veterinary internal medicine textbooks, the decision should be made by evaluating clinical signs alongside laboratory values, rather than relying on numbers alone.

Comparison of dog and cat blood types

Blood type systems vary significantly between species. Before any blood transfusion, we always perform both a blood type test and a crossmatch to ensure compatibility.

Differences in dog and cat blood types

Item	Dogs	Cats
Main blood types	DEA 1 (positive/negative)	Type A, B, AB
Naturally occurring antibodies	None (first transfusion relatively safe)	Present (even first transfusion is risky)
Most common type	DEA 1 positive (frequency varies by breed and region)	Type A (large breed variation; most breeds 70-100%)
High-risk breeds/situations	Sensitization when a DEA 1 negative animal receives positive blood → risk of acute hemolytic reaction on re-transfusion	British Shorthair and Devon Rex have a high frequency of type B
Cross-matching / blood typing	Cross-matching essential for re-transfusion	Blood typing essential from the first transfusion (cross-matching recommended)

In cats, even a first transfusion can cause a fatal reaction within minutes if the blood type does not match.

How is the blood transfusion process carried out?

Blood transfusions are carried out carefully in stages, with the key management principles being “slowly and with close monitoring.”

Blood typing: Both the donor and recipient are tested.

Cross-matching: Major and minor cross-matches are performed to check for agglutination reactions.

Blood preparation: Whole blood or packed red blood cells are warmed to body temperature.

Slow initial infusion: The first 15–30 minutes are administered at a slow rate to monitor for adverse reactions.

Main infusion: If no abnormalities are observed, the transfusion continues at a normal rate over 2–4 hours.

Post-transfusion monitoring: The patient is observed for 24–48 hours for fever, jaundice, and hematuria.

A close-up shot of a cat receiving a blood transfusion.

Warning signs of adverse reactions during transfusion

Transfusion reactions can be life-threatening. If any of the following signs appear during or immediately after a transfusion, stop the transfusion immediately and notify your veterinarian: - Elevated body temperature (fever) - Vomiting or excessive drooling - Difficulty breathing or rapid breathing - Pale or jaundiced gums - Red or brown urine (hemoglobinuria) - Sudden collapse or hypotension In particular, transfusing type A (or type AB) blood to a type B cat can cause fatal acute hemolysis and death within minutes, even with a small volume of about 0.5 mL, due to the strong anti-A antibodies present in type B cats. Conversely, when type B blood is transfused to a type A cat, the anti-B antibodies are generally weaker, so the reaction is often milder; however, the lifespan of the transfused red blood cells is significantly shortened, meaning the therapeutic effect of the transfusion does not last long. Because mismatched transfusions are dangerous in either direction, a blood type test must always be performed before transfusion to select compatible blood.

Post-transfusion care and recovery

Close monitoring is essential even after a blood transfusion. From immediately post-transfusion through the next 24 to 48 hours, periodically check your pet’s body temperature, pulse, respiratory rate, mucous membrane color, and urine color. Delayed hemolytic reactions can occur from 24 hours up to 28 days after transfusion, so carefully observe changes in energy levels and appetite for several weeks following the procedure. Treating the underlying condition concurrently is necessary to maintain the benefits of the transfusion. If a repeat transfusion is required, a crossmatch must be performed again to detect any antibodies sensitized by the previous transfusion. At home, please frequently check your pet’s gum color and respiratory rate.

A puppy recovering comfortably at home after a blood transfusion

How to become a blood donor?

Some pet owners even wish to register their pets as blood donors. Generally, dogs (25 kg or more) and cats (4 kg or more) must be between 1 and 8 years old, fully vaccinated, negative for heartworm and blood-borne infectious diseases, have normal health check-up results, and show no aggressive behavior. Since specific criteria and procedures vary by veterinary clinic, it's best to consult with your veterinarian.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Do puppies also need a blood type test before their first transfusion?

Dogs lack naturally occurring antibodies, so their first blood transfusion is relatively safe, and according to standard veterinary guidelines, blood typing the recipient isn’t strictly required for the initial transfusion. However, DEA 1-negative blood is preferred, and recording the dog’s blood type can help reduce the risk of sensitization reactions during future transfusions. After the first transfusion, sensitization may occur, so a crossmatch is essential before any subsequent transfusions.

Why is a cat’s first blood transfusion risky?

Cats are born with naturally occurring antibodies against blood group antigens they lack. B-type cats, in particular, have strong antibodies against A-type blood, meaning even a small amount of A-type blood can trigger a fatal hemolytic reaction within minutes.

How long does the effect of a blood transfusion last?

The lifespan of transfused red blood cells can vary depending on blood type compatibility and the severity of the underlying disease. If there is a blood type mismatch, the transfused red blood cells may be destroyed very quickly. If the underlying condition (such as hemorrhage, hemolysis, or kidney failure) is not resolved, anemia may recur, so it is essential to address the root cause alongside the transfusion.

How much does a blood transfusion cost?

Costs vary significantly depending on the clinic, location, and volume of blood needed, so please contact your veterinarian directly for an accurate estimate. The total fee typically covers blood typing, cross-matching, the blood itself, the transfusion procedure, and hospitalization for post-transfusion monitoring.

Can a dog that has received a blood transfusion become a blood donor again?

Animals with a history of blood transfusions are generally not selected as donors due to the risk of sensitization. If your pet has received a transfusion in the past, please remember that cross-matching will be even more critical should they need another transfusion in the future.

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References

[1] Feline Emergency and Critical Care Medicine, 2nd Edition

[2] Advanced Monitoring for Small Animal Emergency and Critical Care, 2nd Edition

[3] Kisielewicz C, Self I, Bell R. (2014). Assessment of clinical and laboratory variables as a guide to packed red blood cell transfusion of euvolemic anemic dogs. J Vet Intern Med 28(2): 576–582.

[4] Schalm's Veterinary Hematology, 5th Edition