About feline blood types.

Photo of mother cat lying down nursing her four kittens

Similar to blood groups in humans, cats can also be split into three important blood types of A, B, and AB, which are governed primarily by variants in the CMAH gene. These blood types are determined by molecules on the surface of red blood cells (known as antigens), which are used by the cat’s immune system to determine if the cell belongs or should be destroyed. A cat's blood type will be influenced by both the mother and father’s genetic contributions.

Why blood type is important for cats.

Blood Transfusions

Both type A and B cats are born with some antibodies against other blood types. Notably, type B cats have high levels of antibodies against type A blood. Cats of the rare AB blood type are most versatile, as they can receive both type A and type AB blood transfusions.

Unlike humans, there is no cat blood type that can act as a universal blood donor. If a cat receives a non-compatible blood type during a transfusion, it may cause a severe, life-threatening reaction including fever, kidney failure, and widespread destruction of red blood cells. Prior to all transfusions, cats should be typed and crossmatched to ensure compatibility. Please consider sharing your cat’s blood type with your veterinarian.

Feline Blood Transfusion Compatibility graphic depicting arrows between cats with different blood types. Arrows A->A, AB->AB, and B->B are labeled as whole blood compatible. An arrow from A->AB is labeled as packed blood cells recommended.

For Breeders

During pregnancy, kittens are shielded from their mother’s immune system. However, when kittens begin nursing, they receive some of their mother’s antibodies in her milk.

Type B cats have high levels of antibodies against type A blood, so when blood type A or AB kittens are born to a blood type B mother, these antibodies, when absorbed by the newborn kitten, cause destruction of its red blood cells. This is a potentially fatal reaction called neonatal isoerythrolysis. Kittens of type B mothers with fathers of unknown or A blood type should be bottle fed or foster-nursed, and separated from their mother for the first 24 hours to avoid this reaction, unless blood typing performed immediately following birth shows the kitten to have a compatible blood type to the mother.

Although some blood types are less common and require additional planning, they represent normal genetic variation. It is important that you discuss your cat’s blood type with your veterinarian if you are considering breeding.

Frequency of different feline blood types.

Blood type A is the most common in domestic cats. However, frequencies of A, B and AB blood types vary widely within regional populations of non-pedigreed cats. In Australia, B blood type cats may exceed 25% of the population, while in the United States, they represent less than 6% of the total.

Blood type within pedigreed breeds is much less variable regionally, due the influence of breeding programs. Breeds with high levels of blood type B (over 30%) include the British Shorthair, Cornish Rex, Devon Rex, Exotic Shorthair, Turkish Angora and Turkish Van cats. In contrast, Siamese and related breeds are nearly exclusively type A. Ragdoll cats are unique, and show a relatively high incidence of type AB blood.

Why do different blood types exist?

The variation in blood type antigens in cats are thought to be an evolutionary adaptation to avoid blood-borne infectious disease, much like sickle cells in people of sub-Saharan African descent are thought to be a genetic adaption against malaria.

Current limits of this test.

This test identifies 4 variants (b variants c.269T>A, c.179G>T, c.1233delT and c variant c.346C>T) in the CMAH gene discovered in domestic cat population. Mik antigens also play a role in blood type compatibility, and are not included in this test. Cats carrying undetermined, new, or undiscovered variants in CMAH or other genes may have a different blood type compatibility than that reported by this test. Accuracy of this test at predicting blood type in wildcats or wildcat hybrid breeds has not been determined.

On occasion, cats can have indeterminate genetic blood type results. This may occur when a confident call cannot be made for one or more of the blood variants tested which is often the result of an unusual sequence of DNA in the region tested or due to quality of the DNA sample. Alternatively, this may occur due to an exceptionally rare occurrence of unique genetic rearrangements resulting in the presence of greater than two genetic blood variants. The potential impact on genetic blood type due to these atypical blood variant combinations is currently unknown. In all cases of indeterminate genetic blood type results, standard serologic blood typing will be required to determine the cat’s clinical blood type and associated transfusion and breeding risks. Due to the rare nature of this result, it is an area we are continuing to research. Pet parents with indeterminate blood type results in their cat’s report are encouraged to reach out to our customer service experts about the opportunity to contribute to this research.