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Why is my new puppy's diarrhea getting worse after food change?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Medium (23 - 60lb) | Male | unneutered | 4 months and 13 days old | 23 lbs

Hey there. My 18 week pomsky is having diarrhea. When we first picked him up 9 days ago. We accidentally switched his food without transitioning. He had diarrhea for the first 3 days, went back to solid, and now is having diarrhea again. It seems to be getting worse and is far more liquid like than it was before.

3 Answers

Most Helpful Answer

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Answered By Ana M, DVM

Veterinarian

Published on April 30th, 2018

Thank you for submitting your question regarding Ludo. He will need to see his veterinarian regarding the diarrhea. Being a young puppy, intestinal parasites are common. He could also be experiencing a bacterial imbalance secondary to the diet change and the stress of coming to a new home. His veterinarian will likely perform fecal tests and prescribe a medication and possibly a probiotic. In the meantime, encourage him to drink plenty of water so that he does not become dehydrated from the diarrhea. I hope this information helps!

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Other Answers

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    Answered By Dr. Strydom, DVM

    Veterinarian

    Published on December 27th, 2017

    Any puppy having that much diarrhea needs to be seen by a vet. Diarrhea can make them dehydrated even if they are still drinking water. The reason for the diarrhea could be diet change but it could also be from internal parasites (worms) or it could be from a virus (like parvo). I strongly suggest you get Elsa to a vet for an exam. She definitely needs to be eating puppy food, I can tell you that and really, dry food would be best to give over the canned food. Hope this helps. Best wishes.

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    Answered By Jessica Desrosiers

    Veterinary Technician

    Published on November 16th, 2020

    Poor Piper! There are a number of reasons why she may be having diarrhea. If you just brought her home, stress from being in a new place may be causing some GI upset. If you've also switched her food suddenly, that can also cause GI upset. Feeding the same food she was eating at her old location, or offering a bland meal of boiled chicken and rice and gradually switching over to the new food, as well as giving her a few days to settle in may help settle her stomach. If she is having severe diarrhea, is lethargic or refusing to eat, has other symptoms in addition to the diarrhea, seems dehydrated, or you are seeing blood, worms, or other issues with the stool, then a trip to the vet before your already schedule appointment is a good idea as puppies can quickly become dehydrated if they are ill.

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