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My dog still has worms after two deworming pills. What's next?

Updated on September 23rd, 2025

Pet's info: Dog | Border Collie | Female | spayed | 4 years and 4 months old

Can a dog still have worms after giving them 2 doses of pills not even a week apart?

5 Answers

Most Helpful Answer

Answered By Destini R. Holloway, DVM

Veterinarian

Published on February 28th, 2016

Yes she sure can. It can take up to 1 week to rid the first round of worms in her system. Then as the worms in her system go through their 2 week life cycle (from baby worms to adult worms that you see in the poop) they should be treated again as a re-emergence of worms is seen.

So the deworming schedule that I follow to ensure all worms (baby's and adults) are gone is as follows:

1) Deworm today

2) Deworm again in 3 days

3) Deworm again in 2 weeks

But technically and most of the time you can get away with just doing #'s 1, and 3. Hope this helps!

118Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Dr. Melanie, BVSc MS
Veterinarian
Published on August 28th, 2019
Due to the life cycle of worms, it takes at least two deworming treatments given two weeks apart to kill all the worms. The first treatment kills the adults present while the second treats the worms that had no yet hatched from eggs during the first treatment. I would give Marshall a deworming treatment now, then another in two weeks. That should hopefully kill all the worms.
1Pet Parents found this answer helpful
Answered By Dr. Melanie, BVSc MS
Veterinarian
Published on February 16th, 2017
Yes, Maryjane will be fine! Her pooping out worms is a sign the deworming treatment is working. She will need another deworming treatment in two weeks to make sure all of the worms are killed, then she will need one monthly until she is six months old. After that, she should be dewormed every three months :-)
1Pet Parents found this answer helpful
Answered By Destini R. Holloway, DVM
Veterinarian
Published on December 6th, 2018
Tapeworm medication is specific, so double check to make sure that the dewormer you used was for tapeworms and not just roundworms and hookworms.
It takes up to 7 days for the worms to evacuate out of her system. She can however get re-infected if she eats her own poop, continues to have a flea problem (which is where tapeworms come from) or if she eats another pets poop that has tapeworms.
Tapeworms don't have to be retreated in 3 weeks b/c they just come right out and don't have a life cycle like the other worms do (hookworms and roundworms). If she had other worms, then yes she would need another treatment in 2 weeks, not 3.

I hope this helps and best wishes with your pet Molly moving forward. Take care!
1Pet Parents found this answer helpful
Answered By Laura Johnson VMD
Veterinarian
Published on March 30th, 2018
Hi, thanks for using Petco Pet Education Center, formerly Petcoach!

That's good that you see adult worms, it means the medication is working! I would have your Vet recheck a stool sample in 3 weeks to be sure no eggs are present. The 2 doses may be enough to kill the adult worms. Also he will be started on heartworm prevention that also is a monthly dewormer when you bring him to your Vet to continue vaccines.

Have a great weekend!
1Pet Parents found this answer helpful

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My dog's hookworms came back. When should I give the second dose?

Hi, thanks for using Petco Pet Education Center, formerly Petcoach! Yes, I recommend treating with first round then repeating a round 3-4 weeks after the first. Then her stool rechecked 4 weeks after the 2nd round. Be sure to start your dog on a good heartworm preventative like Intercpetor or Sentinel which can help prevent reinfection with Hookworms. If your dog has been off heartworm preventatives have her tested before restarting. I hope this helps and good luck!

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