Like humans, cats have blood groups such as A or B or even AB. Blood group A is the most common. A cat’s blood group is determined by genes. As a cat, I don’t know why this would be important, but my girl tells me it could be important if the cat needs a blood transfusion and then the blood group will determine if the donor blood can be accepted.

I never knew what my blood group is. It was probably A, but that doesn’t matter now. I don’t need blood where I’m at. I doubt most cats would care what their blood groups are. It’s just not something we think about or even consider.

https://icatcare.org/advice/blood-groups-and-blood-incompatibility/