Feline Blood Typing: A, B, AB and Fatal Mismatch Risk
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Key takeaways
- Feline AB system: types A, B, and AB.
- Type B cats often carry strong anti-A antibodies — tiny volumes of type A blood can be fatal.
- Type A cats usually have weaker anti-B activity, but mismatch still shortens red-cell survival and can react.
- Type AB cats lack anti-A/anti-B alloantibodies, but donor plasma antibodies still matter with whole blood.
- Plasma must be type-matched too.
Inheritance snapshot
Feline AB blood groups are inherited. A is dominant over B; AB reflects a third allele pattern allowing co-expression. You do not need the genetics to type safely — you need a validated kit result before the line is connected.
Product matching rules
| Recipient | Preferred red cells | Notes |
|---|---|---|
| Type A | Type A | Type B donor is wrong |
| Type B | Type B only | Type A may be fatal |
| Type AB | AB ideal; often type A pRBC/washed A | Avoid type B plasma antibodies; cross-match |
If whole blood from A or B is given to AB, donor plasma antibodies can still cause reactions. Packed or washed red cells reduce plasma transfer.
Kit caveats
In-house kits are fast, but discordant AB results have been reported in some FeLV-positive cats with certain kits historically. If the clinical picture and kit disagree, repeat with an alternative method or reference lab before elective transfusion.
Reaction pattern reminder
Acute signs can include fever, tachycardia, tachypnoea, vomiting, urticaria, haemolysis, collapse, and shortened red-cell survival. Stop immediately and support — do not finish the unit “to avoid waste.”
Cross-match guide → · Xenotransfusion caution →
