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Puppy diarrhea after heartworm prevention tablet? What's wrong?

Updated On September 23rd, 2025

Pet's info: Dog | German Shepherd | Male | neutered | 2 months and 20 days old | 110 lbs

My puppy started heartworm prevention tablet and has very loose stools. He eats royal canin dry puppy German Shepherd food. In the morning, I give it to him with a topper for dry food and the rest of the day he eats it dry. Can it be the med that is making his stool so loose

1 Answer

Most Helpful Answer

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Answered By Daniel Fonza, DVM

Veterinarian

Published on July 17th, 2018

Hi there and thank you for using Petco Pet Education Center, formerly Petcoach to address your concern. Sometimes loose stool can develop after taking a medication. I would initiate a bland diet as outlined below and see if this helps. If the loose stools continue, I would recommend switching the food and adding in a probiotic such as Purina Fortiflora, which can be found online or at your local Petco. If the loose stool does not resolve, then I would recommend having a veterinarian examine Max so that the most appropriate diagnostic and treatment recommendations can be made. I hope this helps! Please let me know if you have any other questions or concerns and I would be more than happy to help you further.

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