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How Long After Deworming A Cat Are The Worms Gone?

by Lucy

As gross as it might seem, worms are a common internal parasitic infection that cats suffer from. The only way to deal with this as a cat owner is to deworm your cat regularly, and make sure they are up to date with vet visits.

Worms are such a common problem in cats, especially if they are allowed outdoors, as they can be easily passed from animal to animal, and they can easily pick up worm eggs when exploring outside.

The best way to get rid of worms is to deworm your cat, but how long after deworming a cat are the worms gone? Most deworming medicines take around three days to work, but more severe infections can require more time to work. The type of worm medication and the health of your cat will also determine how long it takes for the worms to be gone after your cat has had the deworming medication.

You most likely have quite a few questions surrounding the topic of deworming your cat, and as a pet owner, it is always best to gather all the information you can, especially when it comes to medication and treating certain infections. To help you, we have covered just about everything you need to know about deworming your cat.

Which Worms Are Treated In Cats?

Intestinal worms are the types of worms that are treated in cats, using deworming medication. Almost every cat will have some sort of worm infection in their life, as they are really easy to pick up. Some feral kittens are even born with worms they contract from their mothers.

Intestinal worms live in a cat’s intestines and can cause them to fall sick if left untreated. In the worst-case scenario, your cat might become so sick from the worm infection that they do not survive.

There are three types of intestinal worms that are most commonly found in cats:


Tapeworms are commonly passed to a cat through the cat eating an infected flea. They are segmented worms that anchor themselves to the wall of the cat’s intestine and grow larger and larger.

Segments of the tapeworm break off as they grow, containing eggs that are ready to infect another animal once passed through the cat’s digestive system.


Hookworms are tiny parasites and it is fairly difficult to even spot them with the naked eye. They attach to the lining of a cat’s intestine and feed off of their blood.

These worms release eggs that travel through the digestive system and which are passed out into a cat’s stool, where they wait to infect the next animal.


Roundworms look quite similar to garden worms, but they are much thinner. Unlike tapeworms and hookworms, they do not attach to the wall of the intestine, and instead, they move around and swim around the inside of a cat’s gut.

Kittens often carry roundworms, as they can be passed through nursing, but they can also be picked up if a cat ingests another infected animal, such as a rodent.

How Do I Know If My Cat Has Worms?

There are some clear signs which a cat displays when they have worm infection. Often, when your cat displays these signs, the worm infection has become quite bad, and you should talk to your vet about deworming your cat as soon as you can.

Worm infections mostly cause gastrointestinal symptoms in cats, but these can present in a few different ways. Here are the most common symptoms that show your cat has a worm infection:

  • Loose stools and diarrhea, which are caused by the worms disrupting normal intestinal function.
  • Unexplained weight loss even though your cat is eating as normal. This is due to the worms stealing away much of the nutrients your cat needs.
  • Increase in appetite as your cat tries to make up for all the nutrients that are being lost to the worms.
  • A bloated abdominal area is caused by the worms, which is a common symptom in kittens.
  • Cat scratching their behind more and scooting along the floor to try and relieve the itchiness.

How Long After Deworming A Cat Will The Medication Work?

You would want the worms to disappear as soon as possible after deworming your cat, but these things can take a little bit of time to work. However, it does help to know how long deworming medicine takes to rid your cat of worms, so you can keep a check that the medication is working.

While you wait for the deworming medication to work, you should try to keep your cat isolated from any possible infectors, and to keep them and the area they are in clean. This will go a long way to prevent re-infection and to prevent any other animals in your home from contracting worms.

Most deworming medications will take around three days to work and to rid your cat of worms, as long as they are not re-infected during this time or just after. However, the time it takes for the deworming medication to work does depend on a few different factors, and more severe infections with substantially large worms might take longer to work.

Severe infections, where there are a greater number of worms and where they are larger, might require up to 9 days for the mediation to work.

Factors That Affect How Long Deworming Medication Takes To Work

There are a few factors that might affect how long deworming medication takes to work, and it can vary from cat to cat.

While in a normal infection, the deworming medication can take three days to fully rid your cat of worms, other factors might cause this to be a little bit longer.

Here are some of the factors that might affect the time that deworming medication takes to work:

Type Of Worms

The type of worm that your cat is infected with does alter how long the medication takes to work, as some worms are a little more stubborn and it takes longer for them to disappear.

The Number Of Worms

If the infection is quite bad and there is a large number of worms infecting your cat, the medication might take longer to work. You might even need a course of medication for your cat, opposed to a single dose, in order to get rid of all of the worms.

The Deworming Medication

Different types of deworming medications can take longer to work than others, so the type of medication used can affect the time. You also need to make sure that the medication you use for your cat is suited to their weight and size, and is also suited to the type of worm they are infected with.

Resistance To Medication

In unfortunate situations, some types of worms can form a resistance to worm medication, and you will most likely need to follow a course of medication to get rid of the worms in this situation. Some deworming medication is stronger than normal, and these might be needed for serious infections.

Can My Cat Be Re-Infected With Worms After Deworming?

Deworming medication should ensure that worms are gone in between 3-9 days, but if you notice that your cat is still battling with an infection after this, it might be because the medication had worked, and then your cat was re-infected with worms again.

Your cat can be re-infected with worms just after they have been given deworming medication, which is why you need to be so careful to keep them away from any possible worm infections.

If you have other pets in your home that could bring in worm eggs from the outside, or who are infected with worms already, then it can be really easy for your cat to become infected. 

Due to this, it is often recommended by vets that you follow up the first dose of deworming medication with a second dose around two weeks after the first, to ensure that absolutely all of the worms disappear. 

This two-week time frame gives the worms enough time to re-infect your cat and grow enough to be eliminated by the medication, but it is not enough time to cause a severe infection in your cat.

How Deworming Medications Work

When looking at how long a deworming medication takes to work for cats, it does help to know how most deworming medications work.

In general, deworming medications are anti-parasitic agents that kill the worms and rid the cat of the infection. While all are anti-parasitic, different deworming medications work in different ways. It does help to know how the medication you are using for your cat works.

These are the two main ways that deworming medication gets rid of worms:


Some deworming medications work by paralyzing the worms and making it impossible for the worms to hold onto the wall of the intestine anymore.

This means that the grip of the worms on the intestine wall is broken, and they can then be passed through your cat’s digestive system until they are expelled through feces. This is a good treatment for tapeworms and hookworms.


Other deworming medications work by absorbing sugar in the gut which the worms require to survive. The worms will die off as they do not have access to this sugar, and then the worms will be passed through the cat’s feces. Roundworms are best suited for this type of deworming medication.

Will My Cat Pass The Worms Through Their Feces?

The unfortunate part of deworming your cat is that you might notice some of the worms in their feces. This is a good sign, as it shows that the worms are dying and then being passed through the stool, but it can be rather unpleasant.

In some cases, you won’t notice worms in your cat’s feces if the infection is not too large, and the medication can still be working even if there are no visible worms in their stool.

For larger infections, you will notice worms in their feces, especially if the infection was of larger worms such as tapeworms.

What you do need to remember however is that eggs are not killed off by deworming medication, and they can still be found in your cat’s feces, which is why re-infection can happen so easily, and why it is recommended to do a follow-up dose two weeks after the first.

Remove any feces from your cat’s litter basket as soon as it appears to try and avoid re-infection. It’s even recommended to immediately replace all of the litter and clean the litter box and surrounding area after your cat has been cleared.

Does Deworming Medication Have Side Effects?

Most deworming medication should not come along with any side effects, especially if the worm infection is mild and the medication has been suited to your cat’s weight and size.

However, your cat might display some digestive side effects after having deworming medication, which will show as the worms are being processed out of their intestines. Some of these symptoms could include a loss of appetite, vomiting, and diarrhea, and maybe even drooling.

If by some chance these symptoms do appear, they should go away within 24 hours. If they do not, you should get hold of your vet to talk about their symptoms. It also is not uncommon for kittens to experience some mild diarrhea and vomiting after deworming, but this should not last long and should not be severe.

Preventing Re-Infection Of Worms

It is so important to put measures in place when deworming your cat to try and prevent re-infection. Here is what you can do to try and prevent your cat from becoming infected with worms again:

Practice Good Hygiene

The best thing you can do to prevent re-infection is to practice good hygiene in the home. Clean out your cat’s litter box daily and replace the litter weekly, or according to the manufacturer’s directions. This is where there is a large risk of re-infection. Wash your hands well after cleaning the litter box as well.

Make sure to wipe down any other surfaces your cat might be in contact with, as they could have worm eggs stuck on their coat or paws, and these can survive a few days out in the open.

Prevent Fleas

Fleas can easily transmit worms to your cat, so treating them for fleas and regularly grooming your cat can lessen this quite a bit. You should also try to keep your cat indoors as much as possible, to prevent them from picking up fleas from other cats.

How Long After Deworming A Cat Are The Worms Gone?

Most deworming medications take around 3 days to work, but severe cases can take up to 9 days for the worms to be gone. Certain factors can alter this time, such as the type of worm infection, the type of medication used, and how bad the infection is.

Re-infection is also a worry after deworming your cat, so most vets recommended a second dose of deworming medication two weeks after the first, to properly rid your cat of worms.

It does help to know the symptoms to look for that your cat has worms, and how to know once the deworming medication has worked, to ensure that your cat is kept as healthy as possible. After deworming your cat, follow good hygiene habits and treat your cat for fleas to prevent a re-infection.

Related Questions

Can I deworm my cat on my own?

You can deworm your cat on your own, but you will need to get proper deworming medication from a vet and follow the right amount of medication you need to give your cat and the routine of medication laid out by the vet. It does help to have a vet identify the type of worm infection your cat has, so the right medication can be used.

Will my cat feel ill after deworming?

It isn’t uncommon for cats to feel slightly ill after deworming, and they might suffer from mild digestive issues. These should only last for a day or so, and anything more should be reported to your vet.

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