Blood Types Cat

Blood types in cats

For cats different kinds of blood types exist, of which the AB-system is the most important one. In this system, cats can have an A, B or AB blood type.
The presence of naturally occurring high amounts of anti-A antibodies in (most, but not all) type B cats, leads to the bursting of type A red blood cells when they get into contact with type B blood. This is for example the case in neonatal isoerythrolysis (NI). NI can occur when a queen with blood type B is bred to a tom with blood type A, giving birth to kittens with blood type A. When drinking colostrum during the first days of life, the kittens absorb the anti-type A antibodies produced by the type B queen. This will lead to the bursting of the kitten’s type A red blood cells, causing anaemia, which can be lethal. It is therefore important for breeders to test the blood type of breeding queens, to identify the risk of NI and minimizing the chances of neonatal mortality.

Genetic test K480

From January 2026 onwards, CombiBreed offers genetic testing for blood typing in cats with one (combined) DNA test, instead of the former three different tests with test code K793, K300 and K330. We decided to do so, to be able to test more different mutations for the b alleles, giving a  more precise result, but also to make interpretation of the results easier. From now on you will receive just one result for the genetic blood type. This is a combination of the results of several mutations for the b and c alleles (c can also be called AB), interpretated for you in the laboratory. This DNA test can be used for all cat breeds, although not in all breeds  the b and/or c alleles are present.

Tested mutations in K480

OMIA variant ID is the number this mutation gets in an internationally used database for genetic disorders and traits in animals (OMIA). The OMIA page for the AB blood typing system in cats can be found here. The use of these OMIA ID’s and variant numbers makes it easier to compare DNA tests between laboratories.

Since additional b mutations yet have to be identified, there is a possibility that the genetic results from this test do not match the conventional blood typing results (serology). It is also  known that the current c variant is associated with type AB blood in Ragdoll cats. Since blood type AB cats from other breeds do not have the Ragdoll type c variant which is analysed with this genetic test (variant ID 799), at least one other variant must be present that also results in type AB blood in other cat breeds. This variant has yet to be identified.

Serologic test K712

Another method to identify cat blood types, is serology. This method does not give information about the genetic background in a direct way and is therefore not suitable to use as a solely method when making breeding choices. When genetic tests do give an inconclusive result, the serologic test can be used to make a distinction between type A or type AB blood and can help to fill out the unknown allele.

Serologic blood typing is mainly used for blood transfusions and can only be performed on whole blood (EDTA or Heparin).

Interpretation of results

Cats with two copies of any of the two b alleles have type B blood. Cats with one copy of any of the b alleles and thus carrier of b have either type A or AB blood, depending on which second allele is present.  If allele c is present next to one of the b alleles, the cat will have blood type AB, since c is dominant over b and causes blood type AB. If neither the b or c allele is present, this will be reported as N. N means that neither of the tested mutations is found and that the cat presumably has the wildtype allele A. In most cases this indeed is the A allele and the cat will have blood type A. Since additional b and c mutations yet have to be identified, there is a possibility that the genetic results from this test do not match the conventional blood typing results (serology).