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Intestinal parasites, commonly referred to as worms, hide inside your cat, silently causing harm. Common intestinal parasites in cats include roundworms, tapeworms, and hookworms. Some, like roundworms and hookworms, can also infect humans.

If your cat has worms, you want to get rid of them fast and prevent them from ever coming back. Deworming medications kill the parasites your cat already has. Parasite preventives stop future infections from taking root so you never have to deal with worms again. But with so many products available, it can be difficult to choose a treatment for your cat.

My knowledge about intestinal parasites and their treatment and prevention is informed by my 20-year career writing and editing for pet and veterinary publications. I also worked as an assistant in veterinary hospitals for eight years, where one of my jobs was conducting fecal tests to look for the presence of worms. Different drugs kill different worms, so you must always visit your veterinarian for a fecal test before giving your cat a dewormer.

For this guide, I selected products based on safety, efficacy, the number of parasites targeted, and products' ease of use. I also used the quick product reference guide published by the independent, nonprofit Companion Animal Parasite Council in my research. Read more about my selection criteria at the end of this guide.

For additional expertise, I interviewed two veterinarians about treating and preventing intestinal parasites in cats: Dr. Herman Jeffer, a veterinarian with Cornwallis Road Veterinary Hospital in Durham, North Carolina, and Dr. Colleen Sawyer, a veterinarian with Rolesville Veterinary Hospital in Rolesville, North Carolina.

Once your veterinarian has determined what kind of worms your cat has, you can use one of the following treatments to get rid of them once and for all. Note that some of these products require a prescription. Learn more about how Insider Reviews tests and researches pet products.

Best broad-spectrum dewormer: Bayer Drontal Broad Spectrum Dewormer, $27.45 from Chewy Bayer Drontal Broad Spectrum Dewormer effectively eliminates several types of intestinal parasites including tapeworms, hookworms, and roundworms. 

Best oral tapeworm dewormer: Droncit Tablets, $4.94 from Chewy One Droncit tablet quickly and safely kills tapeworms in cats and can be given mixed with food.

Best topical tapeworm dewormer: Centragard Topical Solution for Cats, $44.99 from Chewy One dose of Centragard Topical Solution quickly and safely kills tapeworms in cats, treats hookworms and roundworms, and prevents heartworms when given monthly.

Best oral parasite preventive: Interceptor Flavor Tabs, $48.87 from Chewy Given monthly, Interceptor Flavor Tabs prevent heartworms and treat and control roundworms, adult hookworms, and adult whipworms.

Best topical parasite preventive:Revolution Plus Topical Solution for Cats, $129.99 from Chewy Safe for use in kittens as young as 8 weeks, Revolution Plus Topical Solution treats, controls, and prevents more parasites than any other topical product, including roundworms, hookworms, heartworms, fleas, ticks, and mites.

Bayer Drontal Broad Spectrum Dewormer effectively eliminates several types of intestinal parasites including tapeworms, hookworms, and roundworms. 

Pros: Veterinarian recommended, kills several types of worms, safe and reliable, kills all parasites within seven days, low risk for side effects

Cons: Not for kittens younger than 8 weeks old or less than 2 pounds, can be hidden in food but may be difficult to administer if cat doesn't easily take pills

A broad-spectrum dewormer can knock out multiple types of parasites at the same time. We recommend Bayer Drontal Broad Spectrum Dewormer because it is safe, effective, and eliminates all parasites within seven days. No other cat dewormer kills as many different types of worms as Drontal. This dewormer features two powerful active ingredients, pyrantel pamoate and praziquantel, which together cover tapeworms, hookworms, and roundworms.

To administer, place the tablet far back in the mouth until the cat swallows it or crumble and mix into a small amount of wet food. Drontal has a very low risk for side effects and is safe for kittens and cats more than 8 weeks old and ranging from 2 to 16 pounds.

Bayer Drontal Broad Spectrum Dewormer requires a prescription from your veterinarian. Don't skip this step because cats may have other parasites that even broad-spectrum dewormers can't eliminate.

When using a broad-spectrum dewormer like Drontal, cats may require one or more follow-up treatments to make sure all the worms are eliminated. If the cat has fleas, it should also be treated with a flea control product to prevent future tapeworm infections.

One Droncit tablet quickly and safely kills tapeworms in cats and can be given mixed with food.

Pros: Kills tapeworms within 24 hours, easy-to-administer tablet, powerful active ingredient, long-trusted brand name, affordable, single pills available for purchase

Cons: Some cats may experience salivation or diarrhea after taking, not for kittens under than 6 weeks old

Droncit Tablets tackle tapeworm infestations quickly and safely in cats and kittens 6 weeks of age and older. They are conveniently sold per pill, unlike the other tapeworm dewormer we considered, Bayer Tapeworm Dewormer Tablets, which are sold in a three-pack and at a slightly higher cost per pill.

Each tablet contains 23 milligrams of the active ingredient praziquantel, which works to paralyze and eliminate tapeworms within 24 hours. This ingredient is effective against the most common species of tapeworms (Dipylidium caninum and Taenia taeniaeformis), eliminating them in a single dose. The tablet can be fed whole or crumbled and mixed with food.

Because cats can become reinfected by ingesting another flea, effectively eliminating tapeworms requires treating your cat for fleas as well.

One dose of Centragard Topical Solution for Cats quickly and safely kills tapeworms in cats, treats hookworms and roundworms, and prevents heartworms when given monthly.

Pros: Kills tapeworms with one dose, easy-to-administer topical solution, treats and prevents roundworms and hookworms, prevents heartworms when given every 30 days

Cons: Not for kittens less than 7 weeks old or weighing less than 1.8 pounds, not for use in pregnant or nursing mothers 

Centragard quickly and safely treats tapeworms and two other intestinal parasites (hookworms and roundworms) in cats and kittens 7 weeks of age and older. It is a great option for cats that won't take pills. Simply squeeze the liquid in one spot on the back of your cat's neck and allow it to dry. You can use Centragard one time to treat an infestation of tapeworms, hookworms, or roundworms, or give it monthly to keep your cat free from intestinal parasites and also prevent deadly heartworm. 

Centragard contains the active ingredients eprinomectin and praziquantel, which work to kill worms and prevent future infection. These ingredients are effective against the two most common species of tapeworms (Dipylidium caninum and Taenia taeniaeformis), two species of hookworms (Ancylostoma tubaeforme and Ancylostoma braziliense), one species of roundworm (Toxocara cati), and heartworms.

Because cats can become reinfected by ingesting another flea, effectively eliminating tapeworms requires treating your cat for fleas as well.

Given monthly, Interceptor Flavor Tabs prevent heartworms and treat and control roundworms, adult hookworms, and adult whipworms.

Pros: Prevents heartworms; treats and controls roundworms, adult hookworms, and adult whipworms; easy-to-administer flavored tablet, protects for 30 days, safe for kittens as young as 6 weeks of age

Cons: Can be difficult to give some cats oral medications; some cats don't like the taste; doesn't protect against fleas, which transmit tapeworms

Interceptor is a great choice for pet owners who wish to give an oral preventive rather than a topical product because of the many parasites it protects against. In addition to preventing deadly heartworm disease, Interceptor Flavor Tabs treat and control roundworms, adult hookworms, and adult whipworms with the active ingredient milbemycin oxime. Each pill protects for 30 days, and it's safe for kittens as young as 6 weeks of age.

Interceptor is one of only two chewable parasite preventives available for cats — Heartgard being the other option. Unlike Interceptor, Heartgard only treats and controls one other parasite (hookworms) in addition to heartworm.

Give an Interceptor Flavor Tab as a treat or hide it in a small amount of wet food. You must obtain a prescription from your veterinarian to purchase Interceptor. As with all heartworm medications, your cat needs a heartworm test prior starting this preventive and once a year thereafter.

Safe for use in kittens as young as 8 weeks, Revolution Plus Topical Solution treats, controls, and prevents more parasites than any other topical product, including roundworms, hookworms, heartworms, fleas, ticks, and mites.

Pros: Safe for use in kittens 8 weeks and older and weighing at least 2.8 pounds

Cons: Does not kill tapeworms, caution required in cats with a history of neurologic disorders

Our pick for best topical parasite preventive is Revolution Plus Topical Solution because it protects cats against six different parasites — more than any other topical preventive. Revolution Plus beat out the other topical preventive we considered, Bravecto Plus Topical Solution, because it is safe for kittens 8 weeks and older. Bravecto cannot be used for kittens younger than 6 months old. Revolution Plus also kills ear mites, while Bravecto does not.

Revolution Plus treats and controls two intestinal worms: roundworms and hookworms. It also prevents heartworms, treats and prevents flea infestations (killing adult fleas before they can lay eggs), and treats and controls ear mites and three different tick species (black-legged or deer tick, Gulf Coast tick, and American dog tick). It does not kill tapeworms.

Given every 30 days, this monthly spot-on treatment is simple to apply in one spot to the cat's skin between the shoulder blades. The medication, a small amount of liquid, is absorbed through the skin and dries quickly, leaving nothing behind. Unlike some other topical products like Advantage Multi and Bravecto, you do not need to wear gloves to apply Revolution Plus and you can touch your cat after application, even if the product has not completely dried. If you get the medication on your hands, simply wash them with soap and water.

Before choosing a broad-spectrum parasite preventive for your cat, have a conversation with your veterinarian who can advise you on what might be best depending on your cat's lifestyle and what parasites are most common in your area.

You must obtain a prescription from your veterinarian to purchase Revolution Plus. As with all heartworm medications, your cat needs a heartworm test prior starting this medication and once every year after. Revolution Plus should be used with caution in cats with a history of neurologic disorders such as seizures.

Bayer Tapeworm Dewormer Tablets for Cats: This product contains the same active ingredient (praziquantel) as our top choice for tapeworms, Droncit Tablets for Cats, but it's sold in a slightly more expensive three-pack ($5 per pill as opposed to Droncit's $3 per pill).

Profender Topical Solution for Cats: Like Centragard Topical Solution, Profender kills tapeworms, roundworms, and hookworms, but Centragard also prevents deadly heartworm when given monthly. Kittens must be at least 8 weeks old to use Profender while kittens 7 weeks and older can use Centragard.

Heartgard: The only other chewable parasite preventive available for cats, Heartgard (ivermectin) has been on the market a long time and is a safe and trusted heartworm preventive. However, unlike Interceptor, which treats and controls three other intestinal parasites in addition to heartworm, Heartgard only treats and controls one other parasite, hookworms. Heartgard requires a prescription from your veterinarian, as well as a current negative heartworm test.

Bravecto Plus Topical Solution: Bravecto Plus, which contains fluralaner and moxidectin, is an excellent topical product that prevents heartworm, kills fleas and ticks, and treats roundworms and hookworms. One application of Bravecto Plus lasts two months, unlike most topical preventives, which must be applied monthly. One downside to Bravetco is it cannot be used for kittens younger than 6 months old. Category winner Revolution Plus is safe for kittens 8 weeks and older, and treats and controls ear mites, which Bravecto Plus does not. Additionally, Bravecto Plus's label states that children should not touch the application site for two hours after application; Revolution Plus has no such warning. Bravecto Plus requires a prescription from your veterinarian as well as a current negative heartworm test. It should be used with caution in cats with a history of neurologic disorders such as seizures.

Advantage Multi Topical Solution for Cats: Advantage Multi, which contains imidacloprid and moxidectin, prevents heartworms, kills fleas, and treats and controls roundworms, hookworms, and ear mites. Unlike our top pick, Revolution Plus, Advantage Multi does not kill ticks. Its label states that children should not touch the application site for 30 minutes after application, and other pets that might lick the cat must be kept separated; Revolution Plus has no such warning. Advantage Multi requires a prescription from your veterinarian as well as a current negative heartworm test. It is safe for use in kittens 8 weeks and older and weighing at least 2 pounds.

For this guide, I consulted two veterinarians who work at two different Certified Cat Friendly animal hospitals for advice regarding the treatment and prevention of intestinal parasites like tapeworms, roundworms, and hookworms, as well as heartworms and ectoparasites like fleas, ticks, and mites. Although this information guided us in our product selection, our veterinary experts did not specifically endorse any of the products included in this guide.

I also used the quick product reference guide published by the independent, nonprofit Companion Animal Parasite Council while researching for this guide. The CAPC lists all FDA and EPA-approved parasite control products for small animals, including each product's active ingredients and uses.

Safety and efficacy: We only considered FDA or EPA-approved dewormers and preventives for this guide. We then consulted the Merck Veterinary Manual to ensure all ingredients in these products are known to be safe and effective for use in cats and kittens.

Number of parasites treated: In general, the more parasites a preventive product covers, the higher it was rated. 

Ease of use: Products were rated lower if they were more complicated to use than a similar product. For instance, products ranked lower if the pet owner must wear gloves to apply the product or if children and pets need to be kept away from the treated animal for a specified amount of time.

Cornell University veterinarians estimate that as many as 45% of cats have intestinal parasites at any given time. In adult cats, parasite infestations may cause mild to moderate digestive symptoms like vomiting, diarrhea, and gas. However, heavy infestations, especially in kittens, can lead to more severe digestive symptoms, weight loss , anemia, malnutrition, and restricted growth.

"We'll see cats coming in, for example if they've been in a feral situation. They are anemic, bloated, they have chronic diarrhea and vomiting, their coats are brittle and unkempt, and they can be very depressed," Jeffer said. "Kittens can actually die from parasite infestations."

Some of the most common worms seen in cats are roundworms, tapeworms, and hookworms.

Roundworms: Common in cats, especially in kittens, roundworms are large (3 to 6 inches), smooth, and round-bodied. You might not notice symptoms, particularly if your cat has only a few roundworms. In kittens, large numbers of worms may cause a pot-bellied appearance, vomiting, diarrhea, low appetite, dull coat, and restricted growth. You might also see roundworms in your cat's stool or vomit.

Tapeworms: If you see something in your cat's feces that resembles grains of white rice, or you notice them licking or biting the area under their tail, they could have a tapeworm infestation. Cats contract tapeworms when they ingest an infected adult flea. As the tapeworm grows, segments break off and pass in your cat's stool.

"Probably the most common kind of worm that pet owners are going to notice is a tapeworm," Jeffers said. "The cat might have other ailments that need to be addressed, so there are a lot of reasons to bring your cat to the vet to sort out which worm it is and to make sure there aren't secondary issues that are resulting from that infection."

Hookworms: Tiny worms nearly invisible without the assistance of a microscope, hookworms are blood-sucking parasites that attach to the wall of the intestines. Signs of hookworm infection in cats include anemia, weight loss, and dull coat. Hookworm-infested cats also sometimes have dark, tarry-looking stool.

Veterinarians recommend broad-spectrum parasite prevention for all cats. Indoor-outdoor cats are at high risk for contracting intestinal parasites like roundworms, hookworms, and whipworms, and all cats, including those that live indoors, need prevention from deadly heartworms.

"Parasites can enter the house many ways," Sawyer said. "They can be brought in by other pets like the family dog or by small rodents. They can be brought in by us, for example, a flea on our clothes or on our shoes. Mosquitoes can also enter through an open door or window and transmit heartworm disease."

Some owners think their cats only need preventives in the spring and summer, but veterinarians recommend keeping cats on a broad-spectrum parasite preventive all 12 months of the year. Different parasites are active during different months, and parasite activity can vary depending on where you live. Additionally, parasites can become active earlier than expected, including in the winter.

"It's a little bit of a gamble, especially with climate change and the unpredictability of the weather in most areas of the country," Jeffer said. "Where I live in North Carolina, the weather changes from week to week. One week we might have a snowstorm and the next week it might be 70 degrees. When there are puddles on the ground and the temperature's warm enough, that's mosquitoes' favorite time of year."

Outdoor cats are most at risk of picking up intestinal parasites like roundworms and hookworms, as well as heartworms, fleas, and ticks. However, even indoor cats need parasite prevention. Fleas can be brought into the house by other pets or even on your clothing, and cats that live inside can still be exposed to other parasites.

"For cats that are indoors, there's much less of a risk that they might contract one of the intestinal parasites, although my indoor-only cat somehow found a squirrel in our attic and did kill it, so I guess there is always that risk," Jeffer said. "[However], the main risk is heartworms. Even one heartworm can potentially be fatal to a cat. Even if a couple of mosquitoes get into the house that happen to be carriers for heartworm disease, there's a chance that an indoor-only cat can get heartworms and can actually die from it."

In general, Sawyer prioritizes products that provide both flea and heartworm prevention. "Heartworm disease, although rare, is not treatable in cats and has a high fatality rate," she said. "Coverage for ticks, immature life stages of fleas, and intestinal parasites are also important, and fortunately now there are products available that protect against all the above."

If you suspect your cat has worms, always take them to the veterinarian for a physical exam and fecal test, which is an examination of the stool that reveals what type of worms your cat has.

"Generally speaking, if they have one parasite, they'll have multiple parasites," Jeffer said. "If they have roundworms, it's not uncommon to see tapeworms or other worms as well, or 'non-worms' like coccidia."

Certain single-celled microscopic parasites (protozoa), including coccidia and Giardia, cause symptoms similar to those caused by intestinal parasites, but they are not true worms. They require different prescription medications to treat them — dewormers won't help.

Even though some dewormers do not require a prescription, do not skip the vet visit since different drugs treat different worms. Your vet can also determine if your cat may have other health issues that need to be addressed.

"It's important to see your veterinarian so they can identify what parasites are present and then prescribe the appropriate deworming medication," Sawyer said. "Your vet can also explain any risks for human disease, which is also parasite dependent."

Depending on the type of worms found, your cat might also need follow-up deworming and a follow-up fecal exam to make sure no parasites remain. Your veterinarian can also identify any other health issues that might be going on aside from intestinal parasites.

Talk to your veterinarian before using natural dewormers for your cat. "When pet owners are looking for a product for their pet, I think they want research behind it," Jeffer said. "Most of the time you really can't guarantee that from a product that's labeled 'all natural.'"

Jeffer, who said he has serious doubts as to whether natural deworming products are at all effective, points out that conventional, veterinarian-recommended dewormers are not only very effective, but extremely safe to use. "They've all been used over decades and there are very few to no side effects associated with them," he said.

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