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My 7-month puppy missed heartworm medication. Can I start it now?

Updated on September 23rd, 2025

Pet's info: Dog | German Shepherd | Female | unspayed | 7 months and 7 days old | 63.5 lbs

I am a first time dog owner and my vet never prescribed my puppy heartworm medication. I assumed at 6 months they get it but I realized she probably should have been put on a monthly chew at 8 weeks. She is 7 months now is it too late or can I run to the store and put her on heartgard now?

1 Answer

Most Helpful Answer

Answered By Laura Johnson VMD

Veterinarian

Published on December 9th, 2017

Hi, thanks for using Petco Pet Education Center, formerly Petcoach!

It is never too late! At 7 months old I recommend that your Vet test Midna for heart worm disease now. If she is negative start Heartgard then retest her again in 6 months. It takes a heart worm 6 months from the bite of an infected mosquito to mature in to adults and cause a test to be positive. So testing now only proves she wasn't bitten in the first 1 month of life.

I highly recommend year round heart worm prevention for the entirety of the pets life. Getting heart worm disease can be deadly and treating heart worm disease is expensive and can also cause be deadly.

I hope this helps and I wish you and Midna the best.

1Pet Parents found this answer helpful

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