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My dog missed Trifexis dose by 3 days. Is she safe from heartworms?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Medium (23 - 60lb) | Female | spayed | 35 lbs

I missed giving my dog trifexis by three-four days. I've since given her the pill, and I'm thinking she's fine. I just wanted to make sure since she had heartworms before I got her (treated and cured), and I'm also a massive worrier. Thank you!

2 Answers

Most Helpful Answer

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Answered By David Darvishian

Veterinarian

Published on October 2nd, 2017

Hi and thanks for using Petco Pet Education Center, formerly Petcoach! Ellie should be fine. Missing 3-4 days should not be a critical time period when talking about heartworm prevention. Now missing that dose over longer time periods could potentially cause a problem due to the life cycle of the heartworm and what stages the medicine kills, since the heartworm goes through several larval stages once inside a dog or a cat. The best thing to do in your case is exactly what you did, give the dose as soon as you realize you missed it and of course, contact your vet for their advice. Ellie should be fine. Great question though. I wish you the best of luck with her.

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    Answered By Laura Johnson VMD

    Veterinarian

    Published on

    Hi, thanks for using Petco Pet Education Center, formerly Petcoach! It is always better to be safe! Ellie will be fine! We get concerned when dogs miss their doses by 30 days or more. And I am sure you have her tested yearly as well. I hope this gives you some peace of mind! Have a great day!

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