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Why is my adopted cat still sick after finishing antibiotics?

Updated On September 23rd, 2025

Pet's info: Cat | Mixed Breed | Male | neutered | 5 lbs

We adopted a young male cat from the shelter, and a week later he was congested. Sounds like he's hacking a hairball, has a runny nose, and fishy breath. Took him to the vet and was given antibiotics. It's been 2 weeks since he's finished them, was doing much better, but now it's back. He eats, drinks, uses bathroom, and plays like normal, and our other cat shows no symptoms. Not sure whether to take him back to the vet, or give him something else...

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1 Answer

Most Helpful Answer

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Answered By Destini R. Holloway, DVM

Veterinarian

Published on February 24th, 2019

Poor guy. I would have him re-evaluated in this case. It sounds like he may need another round of antibiotics or the same antibiotic given for a slightly longer period of time. It is tough sometimes with kitties with URI's, because without culture we are hoping that our broad spectrum antibiotic will clear up the infection entirely. You also have the option of asking for your vet to do a culture, so that we know exactly which antibiotic will clear things up for Cairo. Your other cats immune system is likely better than Cario's, which is why he/she isn't affected. I would also consider keeping Cairo on anti-viral supplements (Lysine powder) long term to help boost his immune system to hopefully decrease the amount of infections in the future. You can find Lysine at any pet store or online retailer. Best wishes with your pet Cario and I hope that he feels better soon! Take care.

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