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Dr. B.
Dr. B., Cat Veterinarian
Category: Cat Veterinary
Satisfied Customers: 15638
Experience:  Small animal veterinarian with a special interest in cats, happy to discuss any questions you have.
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I have a large cat with what is normally a healthy appetite.

Customer Question

I have a large cat with what is normally a healthy appetite. But since a Friday visit to the vet for a check up and vaccinations, he hasn't been eating much and, when he does, throws up some time later, al though his bathroom habits haven't changed. I was told that was a potential side effect of the vaccines, but now that it's Tuesday night, and he's still throwing up his food, I'm concerned they've gone on too long. Is something wrong or is this normal?
Submitted: 2 months ago.
Category: Cat Veterinary
Expert:  Dr. B. replied 2 months ago.

Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your wee one’s situation, and wanted to help.

Now I share your concern about Spiffy.

While it is possible for them to be a bit under the weather post-vaccine as their body processes the vaccine components, his continued signs make me wary of there having been a subclinical gut infection (ie viral, bacterial) that has been able to gain a foot hold because of the immune system's distraction with the vaccine. Of course, we'd also have to consider a possible non-related issue like dietary indiscretion or foreign body ingestion.

In this case, we do need to tread with care, as we don't want him going completely off his food. Therefore, we'd either want a recheck with his vet for treatment or there are some home care options you can consider to see if you can get him settled. In regards ***** ***** latter, we can try him with an OTC pet safe antacid like Pepcid (More Info/Dose @, or Tagamet (More Info/Dose Here @ Whichever you choose, we’d give this 20 minutes before offering food to allow absorption. Of course, if you give this and he cannot keep it down due to nausea that is usually a red flag that we need to bypass his mouth with injectable anti-vomiting medication from his vet.

Once he is more settled, you can plan to try small meals of a light/easily digestible diet. Examples you can use are with boiled chicken, boiled white fish, or scrambled eggs, or meat baby food (garlic/onion free only) There are also OTC vet diets (ie Hill’s I/D or Royal Canin’s sensitivity) that can be used too. The aim of these diets is that they will be better tolerated/absorbed by the compromised gut. Therefore, it should get more nutrients in and result in less GI upset. As long as improvement is being seen, I usually advise continuing this until the signs are settled, and then weaning slowly back to what you normally feed.

Since dehydration is a risk with vomiting in older cats, we need to keep an eye on his hydration. To check this and make sure dehydration isn’t an issue, there are a few parameters you can test. Further to checking for gum moisture, you will want to make sure his eyes are not looking sunken and that he doesn’t have a "skin tent" when you lift the skin. To see how to check these, you can find a good video HERE ( If you do see any of these signs already, then that would be our cue to have him seen before this becomes an additional issue (especially since its often dehydration that makes them feel unwell).

Overall, I would not assume the vaccine is directly to blame for these prolonged signs. It may have given an ongoing infection he had been managing a chance to overtake the immune system or we may have an unrelated issue. Therefore, we need to tread with care. We can try the above just now but if you find that Spiffy cannot keep that or water down, appears dehydrated already, or doesn’t respond to the above within 12-24 hours; then we'd want to get his vet involved. They can assess his hydration, rule out fever, ensure nothing in his stomach that shouldn't be, or any sinister viruses present. Depending on their findings, his vet can treat with injectable anti-nausea medication +/- antibiotics to get this settled for him.

Please take care,

Dr. B.


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