My kitten is sick after deworming. Is it worms or another illness?
Updated On September 23rd, 2025
Pet's info: Cat | American Shorthair | Male | unneutered | 2 months and 6 days old
My 8 week kitten just had his first deworming 3 days ago but now he appears very sick. How can I tell if he has intestinal worms or something else?
5 Answers
Most Helpful Answer
Published on September 7th, 2016
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.
17Pet Parents found this answer helpful
Related Answers from Veterinarians
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Published on February 19th, 2019
Yes, this can be caused by the medication and subsequent killing of the worms. Keep an eye on this kitten, and if it becomes lethargic, anorexic, continues to vomit, or keeps having diarrhea, take it into a vet right away.
1Pet Parents found this answer helpful
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Published on May 17th, 2015
This is common. It may taste bad or you may have forced him to take it. Most likely you could give him another dose with some food but consult your vet first. I am more concerned about what type of worms he has and if you have had a fecal test performed.
11Pet Parents found this answer helpful
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Published on September 15th, 2019
The cats need to see a vet. We cannot diagnose worms based on your description. I suggest you get the cats to a vet so you can get a proper diagnosis of what type of worms they are and then they can be properly treated. Over the counter dewormers do not treat for every possible type of worm a cat can have. You need the diagnosis so the appropriate dewormer can be given. If they are vomiting worms they have a high worm burden and the blood is very concerning.
1Pet Parents found this answer helpful
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Published on June 1st, 2017
Hello It is unusual for worms to cause vomiting in a cat Crowley's age. While most OTC dewormers are safe it may not solve his vomiting. Other considerations for vomiting include a foreign body, dietary indiscretion (eating something that doesn't agree with his system), liver disease, an infection and some other rarer diseases. If Crowley's vomiting continues or he has any signs of pain, decreased appetite, diarrhea or weakness he should be examined by a veterinarian to make sure nothing else is going b with him.
1Pet Parents found this answer helpful
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