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Why is my kitten vomiting yellow and not eating after dewormer?

Updated on September 23rd, 2025

Pet's info: Cat | Domestic Shorthair | Male | neutered | 2 months and 5 days old | 5.73202 lbs

Hi I took my kitten for the 2nd time to the vet this week and he still won't eat or drink, Dr did not find any infection so what do I do now? His been like this for two days and he vomited twice yellow liquid. The vet just keeps giving him medicine that helps with vomiting, he suspects the revolution dewormer was too strong. ... please help

4 Answers

Most Helpful Answer

Answered By Ana M, DVM

Veterinarian

Published on November 19th, 2018

Thank you for submitting your question regarding your kitten. If he is not improving, then I recommend that he has a further work up. He should have fecal testing, blood work and x-rays of his abdomen to determine the cause of his vomiting and inappetance. Kittens can react to deworming medication, but it is typically a short lived reaction. It worries me that he is still ill. There is likely another another disease process present. In the meantime, encourage him to drink so that he does not become dehydrated. I hope this information helps!

1Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Vanessa Yeager DVM MPH
Veterinarian
Published on April 7th, 2020
Hi and thanks for posting.

I would be sure to recheck a fecal test with your veterinarian. Certain parasites and intestinal worms take several round of dewormer to completely get rid of. A follow up fecal test will be able to determine whether or not Larry has cleared the infection.

I hope this helps!
1Pet Parents found this answer helpful
Answered By Dr. Melanie, BVSc MS
Veterinarian
Published on January 8th, 2017
You are correct that the vomiting could be due to the worms, but deworming treatments can also cause vomiting as a side effect. It's serious that he isn't eating or drinking. When a cat stop eating and drinking, it is time to see the vet as Lucky could get dehydrated quickly. I would have Lucky seen by a vet now who can treat his symptoms.
1Pet Parents found this answer helpful
Answered By Dr. Melanie, BVSc MS
Veterinarian
Published on February 25th, 2019
It could be from the dead worms moving through Stich's GI tract, but it could have another cause such as a GI illness. Whenever a dog is both vomiting and having diarrhea, it's time to see a vet. I'd take him into one first thing in the morning. I hope this helps.
1Pet Parents found this answer helpful

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My kitten is sick after deworming. Is it worms or another illness?

Poor Frodo! Some cats do vomit during deworming due to the strength of the medication combined with the parasites moving through the GI system. These side effects should only last a few days, so if it's been longer than that, I would be concerned that it could be due to something else, such as a GI illness, a foreign body, or pancreatitis. I recommend withholding food for 12 hours, then feeding a bland diet of boiled white meat chicken (no bones) in small amounts several times a day for a couple of days. Then slowly add back in his normal diet. If the vomiting continues in the absence of food, he vomits the bland diet, develops diarrhea, stops drinking water, starts vomiting water, or becomes very lethargic, he will need to see a vet right away.

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