Blood Types Cat

Blood types in cats

Cats can have multiple blood types. In this blood type system, cats can have an A, B or AB blood type, of which the AB-system is the most important one. The wildtype variant (A) is the most common blood type and dominant over variant b and c.

Starting in January 2026, CombiBreed offers one combined DNA panel (K480) for genetic testing of blood groups in cats. This replaces the previous three tests (codes K300, K330, K793) and means that the breeder no longer needs to do comparisons and interpretation. The new test panel is more sensitive and detects all three known b alleles (b1, b2, b3) and the c allele.

Note: OMIA variant IDs are internationally standardized by the Online Mendelian Inheritance in Animals (OMIA). This allows easier comparisons between panels run in different laboratories.

CombiBreed Cat Blood Group Typing Reporting

The new reports of K480 Blood Type AB DNA test differentiate between the genetic and phenotypic results. The genetic result indicates the variants that have been detected (A, b1, b2, b3, c), and the phenotypic result indicates the expected blood type and what the cat is carrying.

*The report says ‘Most likely A, (carrier of b/AB)’, what does this mean?

‘Most likely A’ does not mean the test is inconclusive. Like most genetic tests, the wildtype (normal) is assumed when no deviating alleles are detected, so N/N is designated as blood group A. If the result says N/b1, it means one deviating allele, b1, has been detected. No other deviating allele has been detected, so the result is N/b1, or A carrying b. This carries through in the vast majority of cases.

However, serological (blood) testing shows that within the blood type system there are undiscovered variants. There are cats that have blood type B in serological testing, that only carry one b allele in genetic testing; there are also cats with AB blood type that do not possess the known c allele, which has only been found in Ragdoll cats. This means that there must be at least one other b variant and one other c variant that can result in the B and AB blood types. Until these are identified and possible to detect, we cannot with 100% certainty say that a cat is blood type A with genetic testing only. This is true for all genetic testing laboratories at the current time and is true with all types of genetic tests.

There can always be new variants which occur in animals which are therefore not yet detectible. We point it out here specifically because we know concretely that the other deviating alleles exist, and serological testing can help clarify the situation if there is any concern. Cats with B or AB blood groups are considered certain because they must have two deviating alleles to be that blood group.

Neonatal isoerythrolysis (NI)

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 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.

Relevant tests

• K480
• K712