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Why is my dog sluggish and not eating after heartworm treatment?

Updated On September 23rd, 2025

Pet's info: Dog | Shih Tzu | Female | spayed | 14 lbs

Sunday we took my dog to the vet for check up & shetested positive for adult heart worms. We decided to take immediate action and start treatment. She also received shots done on Sunday as well. We started her on the antibiotic and steroid monday. Since then I noticed that she has been herself. I know that we have to restrict her activity & keep her from doing to much movement but I feel like she's gotten really sluggish.She's been eating very little but drinking a lot of water. is this normal?

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2 Answers

Most Helpful Answer

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Answered By Dr. Melanie, BVSc MS

Veterinarian

Published on July 5th, 2017

I'm sorry Aria has heartworms! The fact that she is lethargic and has a decrease in appetite is concerning, and this can be due to the sudden death of a large number of worms from the treatment. When a dog becomes lethargic as well as has a significant decrease in appetite, it's recommended to have them seen by a vet right away. I would take her into an ER vet clinic; if there isn't one in your area, there will be a vet on call for emergencies. The information to reach that vet is found on a clinic's answering machine or website. She needs to be checked out by a vet to make sure everything is ok. I hope this helps and that she feels better soon!

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    Answered By Lauren Barry, BVSc, MRCVS, DVM

    Veterinarian

    Published on

    Im sorry to hear that Aria has heartworms but I'm very glad you're moving forward with treatment. The prednisone she's on will make her thirst increase and urinate more. They may also affect her energy and sometimes behavior. This may be why she's acting differently. Also the heartworms themselves will affect her circulation, as they die off they can cause obstructions in her veins, leading to her feeling unwell. Im sure your Banfield vet will be happy to discuss any concerns with you further, give them a call tomorrow to see if they'd like to examine her sooner than her next scheduled visit.

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