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Is my kitten's lethargy and not eating normal after first vaccines?

Updated On September 23rd, 2025

Pet's info: Cat | Mixed Breed | Female | unspayed | 2 months and 15 days old | 4 lbs

Kitten, F, 11 weeks. Usually crazy amounts of energy, lots of running and jumping, super into food. Last week we got a sibling, another F, 12 weeks. No change in 11 week old's behavior. 7/17 we took 11 week old to vet for first round of vaccines. Since then she has been timid, won't play, barely eating, and sleeping a ton. The vet said that side effects are normal but this seems excessive. Any advice?

3 Answers

Most Helpful Answer

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Answered By Dr. Melanie, BVSc MS

Veterinarian

Published on July 20th, 2020

Thank you for contacting Petco Pet Education Center, formerly Petcoach with your question about Milo. I agree, this does sound a bit excessive to me. I think if she is still acting this way in another 24 hours, I would take her back into the vet to get checked out again. I hope this helps!

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    Answered By Dr. Strydom, DVM

    Veterinarian

    Published on November 30th, 2017

    It could be a vaccine reaction. I strongly suggest you get Crash examined by your vet. He may have a fever and be dehydrated which is going to make him worse. Your vet can give him some medications and fluids to make him feel better sooner. Cats cannot go very long without eating before they get very sick. With him being so young/small that can happen sooner. Please get him to your vet ASAP.

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    Answered By Daniel Fonza, DVM

    Veterinarian

    Published on August 8th, 2017

    It is possible he may be having a low grade reaction to the vaccine or this is completely coincidental to the time of having the vaccine and something else is going on. Sometimes we see slight lethargy and soreness from the vaccines. If Haggis is not improving and only worsening, I would have your vet recheck him to ensure nothing else is going on. Please feel free to contact me with any further questions / concerns you may have. I am also available via consultation.

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