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What normal side effects should I expect after dog heartworm shots?

Updated on September 23rd, 2025

Pet's info: Dog | Mixed Breed Small (up to 22lb) | Male | neutered | 9 years and 7 months old | 11 lbs

Side effects that are normal for dog to experience after heartworm treatment shots?

1 Answer

Most Helpful Answer

Dr. Melanie, BVSc MS

Answered By Dr. Melanie, BVSc MS

Veterinarian

Published on April 18th, 2018

Side effects can be common after heartworm treatment shots. You can see soreness and swelling at the site of the injection, and abscesses can form over time in this spot. Definitely let your vet know of Charlie is very uncomfortable or if his condition appears to be worsening over time. The most severe problems are related to the sudden death of large amounts of heartworms. Get Charlie into a vet right away if you notice a cough or a pre-existing cough becomes worse, he has difficulty breathing, pants excessively, becomes weak or lethargic, collapses, he has a significant drop in exercise, he starts vomiting, drools a lot, or has diarrhea. Best of luck, I hope this helps!
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