How Long After Deworming a Cat Are the Worms Gone?

Written by

Amy Sawy

Veterinarian. DVM


Joseph M. Plummer

Veterinarian, DVM, MVZ

how long after deworming a cat are the worms gone

Do I need to deworm a cat again?

As a pet owner, you should know that worms are among the internal parasitic infections cats often experience. The best means to get rid of these troublesome worms is through deworming.

That raises another concern. Just how long after deworming a cat are the worms gone? The answer: it can take three days to three weeks for the deworming to take effect.

How Long Does It Take for the Deworming in Cats to Take Effect?


As a cat parent, you probably need to know how long will the worm medicine take to work on cats. Will the effect be instant or not?

Usually, the waiting game can take up to 3 days to 3 weeks. The deworming medication can take only days to effect, but it might take longer to work entirely with more severe cases and infections.

Also, certain factors can help determine how long a dewormer takes to work in kittens and adult cats. The time can depend highly on the type of worm and medication.

Depending on the type of worm


Worms are parasitic nightmares that live within a cat’s body and make them ill. If left unaddressed or untreated for too long, they can, unfortunately, be fatal. As a pet owner, there are three types of parasitic worms you should be aware of:

  • Hookworms


The time needed to expel hookworms mostly depends on the dewormer medication. Using a dewormer with Fenbendazole, a common ingredient for hookworm medication, can take 3-5 days to fully eradicate the worms.

  • Tapeworms


Through treatment, tapeworms can easily and quickly be treated with dewormers. After proper deworming treatment, these worms should be eliminated after three days.

  • Roundworms


Roundworms can take longer to eliminate. These parasitic worms tend to be more resistant and stubborn against dewormers. At most, it might take 3 weeks for full resolution.

Depending on the type of dewormer used


Aside from worm type, another thing to note is the dewormer medication used on your cat.

Worms are eradicated by various dewormer medications, each with its level of effectiveness on a particular worm species. The dewormer type will significantly affect the outcome and results of the treatment.

To give you better insight, here is a table detailing which medications are effective for certain worms! Note that these are active ingredients and not the brand itself.

Deworker Hookworms Tapeworms Roundworms
Praziquantel Not effective It takes 1-2 hours to take effect, 2-3 days to be visibly noticeable, and 3-9 days to resolve. Not effective


It takes 1-2 days to take effect after treatment and 3-9 days to be resolved. Not effective It takes 1-2 days to take effect after treatment and 3-9 days to be resolved.
Fenbendazole 3-5 consecutive days of treatment. Some may need a 2nd treatment. Only effective for specific tapeworm types. 3-5 consecutive days of treatment. Some may need a 2nd treatment.
Pyrantel pamoate Need 2-3 treatments, typically set 2-4 weeks apart. Not effective Need 2-3 treatments, typically set 2-4 weeks apart

Knowing what was used can help tell you how fast a dewormer works. Just note that certain deworming medications are explicitly made for certain types of parasitic worms.

For tapeworms, praziquantel and fenbendazole seem the most effective. The former medication treats taenia and dipylidium, while fenbendazole is recommended primarily for taenia tapeworms.

Now, how long does tapeworm medicine take to work in cats? The answer varies, though they usually take effect after three days.

On the other hand, Roundworms require more aggressive dewormer medication and may need a few extra doses for complete eradication. The most common medication ingredient are fenbendazole, milbemycin, moxidectin, and pyrantel.

Lastly, hookworms are most commonly treated with fenbendazole, which is given to cats for 3-5 days to ensure that all worms are expelled.

Also, note that if a cat died after deworming, a possible reason could be overdosing. Remember that overdosing on deworming medication is highly toxic to cats.

Factors Affecting the Time It Takes for Dewormers to Work in Cats


Aside from type of worms and medication, a couple of other factors can affect the period of deworming a kitten or adult cat. Usually, it varies from cat to cat.

With common infections, getting your cat entirely worm-free can take about three days. For severe cases, it can take longer.

See below the factors that can affect how long a cat’s deworming process is!

1. Number of worms

The number of parasitic worms in your cat’s body can majorly affect the duration it takes for the deworming to kick in. Cats with severe infections will take longer for the worms to leave their systems altogether.

Some cats may even need a few doses to eradicate the worms.

2. Resistance to medication

Unfortunately, some worms are resistant to certain types of medications. If the cat still has worms after deworming, it will likely need a follow-up course of dewormer medication to eliminate the worm situation.

Though, how do i know if dewormer is working on cat, you might wonder. You will know if the medication is running its course if you see many dead or dying worms in your cat’s feces.

Tips to Reduce Risks of Re-infection in Cats



Here are a couple of valuable tips to reduce the re-infection in your cats:

  • Follow the flea prevention regimen provided by the vet.
  • Make sure your pet stays indoors, mostly to stop them from hunting or eating infected insects, small animals, and rodents.
  • Remember to wash your hands thoroughly after playing with your cat.
  • Keep cats separated after deworming. You should isolate the dewormed cat from your other cats or pets for at least 3-4 weeks during treatment.
  • Empty your cat’s litter frequently and disinfect their food and water bowls after every use.
  • Wash all your pet’s pillows or blankets and remove all leaves, straws, or any other organic wastes to prevent fleas.

Frequently Asked Questions


Now, onto the frequently asked questions about deworming cats and how long they take effect!

Do I need to deworm a cat again?

Severe worm infections and certain medications might require your cat to undergo several administrations of dewormer to treat your cat’s worm situation. If you notice any more symptoms indicating that your cat is still sick after the deworming, it would be best to consult your vet.

If a cat or kitten still has worms after deworming, they might need deworming again. Alternatively, the vet may suggest a stronger deworming treatment.

How often should I deworm my cat?

Mature cats should be treated at least about four times a year; each turn is three months apart.

Kittens, on the other hand, are a different case. If they have never been dewormed, it is best to consult a vet to get an appropriate deworming schedule.

What to expect after cat deworming?

It would be best to look for any potential side effects. Some cats vomit after taking the medication, while others experience worse side effects like a sensitive stomach, diarrhea, loss of appetite, and increased salivation.

What happens to the worms when you deworm a cat?

You might notice that the worms in cat poop after deworming are either dying or already dead. Though, some persistent ones do come out alive.

Ensure you care for your cat to prevent the worms from returning after a few weeks or months.

How long will the bayer tapeworm dewormer take to work?

One administration of the Bayer Tapeworm Dewormers is enough to treat cats infected by worms. Three weeks is the typical time it takes for your cat’s worm situation to be resolved completely. However, in some cases, it might take longer, up to 5 – 6 weeks.


Hopefully, you finally got an answer to how long after deworming a cat are the worms gone. These parasitic worms usually take three days to three weeks to be eradicated. The time will mostly depend on factors like the worm type and medication used.

Deworming a feline is essential to ensure that they remain healthy and happy. Knowing how long the deworming process takes can help you gauge the effectiveness of the routine and treatment!

Consult a vet to know the appropriate procedure and steps for safe deworming!

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