For the past month our local radio station has been bombarding us with adverts asking us to give blood due to increased need over the holidays. My husband and I ignored them at first but then eventually gave in. On the way home after giving blood, we started talking about cats donating blood and I realised it had been ages since I’d seen a feline transfusion. They are relatively uncommon, especially in general practice, but it’s an interesting subject so I thought I might look into it a bit further. Hopefully your cat will never need one, but if they do (or if you’re just curious about the whole process!), here’s a little bit about what goes on behind the scenes. Why would a cat need a blood transfusion? The main reason why cats get blood transfusions is because they are severely anaemic, which means they don’t have enough red blood cells in their blood. Red blood cells are responsible for carrying the body’s oxygen, so not having enough of them leads to serious problems. Anaemia can occur for three main reasons – not enough red blood cells are produced (problems with the bone marrow or chronic diseases such as cancer), too many are lost (major bleeding after an injury or surgery), or too many are destroyed (autoimmune disease or poisoning). Mild anaemia is not a problem and the cat’s body will usually recover on its own, but severe red blood cell loss either needs to be treated or else it can end in euthanasia. Sometimes medication is enough to fix the anaemia, but occasionally the lost blood cells need to be replaced. The way we measure red blood cells is called PCV (packed cell volume), also sometimes referred to as HCT (haematocrit), and transfusions are only really indicated when that number gets below 12-14% along with clinical signs. If a cat has a disease that can be treated such as infection, autoimmune disease or severe bleeding, then a transfusion may be performed but if their condition cannot be fixed, such as most cancers or end-stage chronic kidney disease, then it probably won’t. Do cats have different blood types? Yes. Just like people, cats have different blood types and giving the wrong one can have disastrous consequences. Feline blood types are called A, B, or AB, similarly named to those in people but entirely different chemically, and the difference between them is the type of chemical called an antigen that the cells have on their surfaces. The cat’s body knows to leave cells with its own antigens alone but to kill off cells that have the other type of antigen, so giving the wrong type of blood will not only result in severe inflammatory disease in the cat but also the immediate destruction of the new cells that have just been given. Therefore, it is essential that all cats be blood typed prior to donating or receiving blood (unlike dogs, who are not as picky for their first transfusion). Most cats worldwide are type A, fewer are type B, and very few are type AB. Interestingly, certain breeds are more likely to have certain blood types, with most Siamese having type A and most Devon Rex having type B. Most standard domestic shorthair cats are type A. There are other variations in feline blood, such as Mik positive or negative, which can cause reactions but these are less well studied and it is not yet possible to test for them. If any sort of mismatch is suspected, then a drop of the donor’s blood is mixed with a drop of the recipient’s blood on a card and the cells are monitored for a reaction. Where does the blood for transfusions come from? Although there are some feline blood banks in the US, most feline blood transfusions in the UK come directly from donor cats at the time it is needed. Donor cats, who are often staff pets but if your cat is big and healthy there’s no reason why they couldn’t donate, should be at least 4 kg but preferably over 5 kg in weight and must not have donated blood in the past 2 months. They should also be fully vaccinated, screened for infectious diseases and not on any medications. Potential donors are given a full physical exam and blood test to ensure they are healthy enough to give blood, and a blood type is done. Once they have passed all of these tests, they are usually sedated and approximately 50-60 ml of blood is collected from the jugular vein in the neck over about 10-15 minutes, followed by the administration of IV fluids to help replace some of the lost blood volume. The blood can then be stored in the refrigerator for up to 24 hours because it is mixed with an anti-coagulant to keep it from clotting. How is a blood transfusion given? The blood from the donor cat is then attached to an IV fluid line and filter and given very slowly into the patient’s vein. The recipient cat needs to be watched very carefully for any sign of reaction such as fever, changes in heart rate or changes in blood pressure. The whole process usually takes several hours and the cat is checked regularly throughout. The prognosis for any cat given a blood transfusion depends much more on the underlying condition than the transfusion itself, but it can significantly improve survival for cats with certain kinds of conditions. Feline blood transfusions are most commonly done in large referral centres, but as there is no special equipment needed they can be done in general practice as well. Because of the time and cost associated with screening both donor and recipient cats, as well as the collection and transfusion process itself, blood transfusions are very expensive and therefore not often chosen by the owner even if they are on offer. But as veterinary medicine progresses and we become more comfortable with the process, it will hopefully become a more practical option in the future. If you are worried about any problems with your cat, speak to your vet or try our Interactive Cat Symptom Guide to help decide what to do next.