Finding worms in your dog’s poop is one of those moments where you simultaneously feel disgusted and relieved - disgusted for obvious reasons, and relieved because at least now you know what you’re dealing with. Intestinal parasites are extremely common in dogs, and the right dewormer takes care of most of them quickly and affordably.
But here’s where it gets confusing: there are multiple types of worms, and no single product kills all of them. The dewormer you grab at the pet store might handle roundworms but do nothing for tapeworms. The one your vet prescribes might cover four types but miss a fifth. And then there’s heartworm, which is a completely different category and requires its own prevention protocol.
This guide breaks down the types of worms that infect dogs, which dewormers treat which parasites, my top product picks, and a prevention schedule that keeps your dog protected year-round.
Disclaimer: Internal parasites can cause serious health problems, especially in puppies and immunocompromised dogs. If you suspect your dog has worms, consult your veterinarian for proper diagnosis and treatment. Some parasites (particularly heartworm) require prescription treatment and cannot be safely treated with OTC products. This guide is informational and not a substitute for veterinary care.
Types of Worms in Dogs
Before you buy a dewormer, you need to know what you’re treating. Each type of worm requires different active ingredients.
Roundworms (Toxocara canis, Toxascaris leonina)
Roundworms are the most common intestinal parasite in dogs, especially puppies. They look like spaghetti - long, white, and often visible in stool or vomit. Puppies can be born with roundworms (transmitted from the mother in utero or through nursing), which is why puppy deworming protocols start as early as two weeks of age.
Symptoms: Pot-bellied appearance (especially in puppies), vomiting, diarrhea, dull coat, visible worms in stool or vomit, weight loss despite normal appetite.
Transmission: Ingesting contaminated soil, feces, or infected prey (rodents). Also transmitted from mother to puppies.
Zoonotic risk: Yes. Roundworm eggs can infect humans, particularly children, causing a condition called visceral larva migrans. This is a real reason to take deworming seriously.
Tapeworms (Dipylidium caninum, Taenia spp.)
Tapeworms are segmented worms that attach to the intestinal wall. You’ll typically see the segments - which look like grains of rice or sesame seeds - in your dog’s stool, around their rear end, or on their bedding. The segments dry out and become harder to identify, so check fresh stool.
Symptoms: Scooting (dragging rear on the ground), visible segments near the anus or in stool, weight loss, and sometimes mild diarrhea.
Transmission: The most common tapeworm (Dipylidium) is transmitted by ingesting infected fleas. Your dog swallows a flea during grooming, and the tapeworm larvae inside the flea develop in the intestine. This is why flea prevention and tapeworm treatment go hand in hand.
Important: Standard broad-spectrum dewormers (the ones that treat roundworms and hookworms) do NOT kill tapeworms. You need a dewormer containing praziquantel specifically for tapeworms.
Hookworms (Ancylostoma caninum)
Hookworms are small, thin worms that attach to the intestinal lining and feed on blood. They’re more dangerous than roundworms because they can cause significant blood loss, especially in puppies, leading to anemia.
Symptoms: Dark, tarry stool (from blood), weight loss, weakness, pale gums, poor coat condition. Severe hookworm infections in puppies can be fatal.
Transmission: Ingesting larvae from contaminated soil, skin penetration (larvae can burrow through the paw pads), and transmission from mother to puppies through nursing.
Zoonotic risk: Yes. Hookworm larvae can penetrate human skin, causing cutaneous larva migrans (itchy, winding skin lesions).
Whipworms (Trichuris vulpis)
Whipworms live in the large intestine and cecum. They’re harder to diagnose because they shed eggs intermittently, so a single fecal test might miss them. They’re also harder to eliminate from the environment because the eggs are extremely resistant and can survive in soil for years.
Symptoms: Watery, mucus-covered diarrhea (sometimes with blood), weight loss, and general poor condition. Light infections may show no symptoms.
Transmission: Ingesting contaminated soil or water.
Heartworms (Dirofilaria immitis)
Heartworms are in a different category from intestinal worms. They’re transmitted by mosquitoes, live in the heart and pulmonary arteries, and can be fatal. Heartworm disease is widespread across the United States, with the highest prevalence in the Southeast, but it’s been diagnosed in all 50 states.
Symptoms: Cough, exercise intolerance, fatigue, weight loss, difficulty breathing, swollen abdomen (from heart failure). Early infections may show no symptoms.
Treatment: Heartworm treatment is complex, expensive ($1,000-$3,000+), and carries real risks. It involves injectable medication (melarsomine) administered over several months, with strict exercise restriction. Prevention is dramatically easier, safer, and cheaper than treatment.
Heartworm prevention is prescription-only and should be given year-round in most of the U.S. Common preventatives include ivermectin-based products (Heartgard), milbemycin (Interceptor), and moxidectin (ProHeart).
OTC vs. Prescription Dewormers
Understanding the difference saves you time and money - and potentially your dog’s health.
Over-the-Counter Dewormers
OTC dewormers are available at pet stores, farm supply stores, and online. They typically contain one or two active ingredients and target the most common intestinal worms.
Common OTC active ingredients:
- Pyrantel pamoate - treats roundworms and hookworms. This is the most common OTC dewormer ingredient and is quite safe.
- Fenbendazole - a broad-spectrum dewormer that treats roundworms, hookworms, whipworms, and some tapeworms (Taenia species, but NOT the most common flea-transmitted tapeworm Dipylidium). Sold under the brand name Panacur.
- Praziquantel - specifically targets tapeworms. Often sold as a standalone tablet.
What OTC dewormers are good for: Treating known roundworm or hookworm infections in otherwise healthy adult dogs. Routine maintenance deworming.
What OTC dewormers can’t do: Treat heartworms. Treat all types of tapeworms reliably. Handle complex or heavy parasite loads. Diagnose which parasites your dog actually has.
Prescription Dewormers
Prescription dewormers are obtained through your veterinarian and often combine multiple active ingredients for broader coverage.
Common prescription products:
- Drontal Plus (praziquantel + pyrantel + febantel) - treats tapeworms, roundworms, hookworms, and whipworms. This is the closest thing to a “treat everything” intestinal dewormer.
- Interceptor Plus (milbemycin + praziquantel) - monthly heartworm preventative that also treats roundworms, hookworms, whipworms, and tapeworms.
- Heartgard Plus (ivermectin + pyrantel) - monthly heartworm preventative that also treats roundworms and hookworms.
- Simparica Trio (sarolaner + moxidectin + pyrantel) - monthly chewable that covers heartworm, fleas, ticks, roundworms, and hookworms.
When you need a prescription dewormer: When your dog has heartworms, when you don’t know which parasite you’re dealing with, when OTC treatment hasn’t resolved the issue, or when you want combination products that cover multiple parasites plus heartworm prevention.
Top Dewormer Product Picks
Here are my recommendations organized by use case. Prices are approximate and may vary.
Best Broad-Spectrum OTC Dewormer: Panacur C (Fenbendazole)
Panacur C is the most versatile OTC dewormer available. It treats roundworms, hookworms, whipworms, and Taenia tapeworms. It’s given as a powder mixed with food over three consecutive days.
- Active ingredient: Fenbendazole
- What it treats: Roundworms, hookworms, whipworms, Taenia tapeworms
- What it doesn’t treat: Dipylidium tapeworms (the most common type from fleas), heartworms
- Format: Powder packets (1g, 2g, or 4g based on weight)
- Dosing: Once daily for 3 consecutive days
- Price: Approximately $10-$30 depending on dog size
- Notes: Very safe with a wide margin of error. Safe for puppies 6 weeks and older. The go-to recommendation for general-purpose deworming.
Best OTC Tapeworm Treatment: Bayer Tapeworm Dewormer (Praziquantel)
If you’ve identified tapeworm segments (rice-like pieces in stool or around the rear), this is the targeted treatment. Praziquantel specifically kills tapeworms, including the common Dipylidium species.
- Active ingredient: Praziquantel
- What it treats: Tapeworms (Dipylidium caninum and Taenia pisiformis)
- Format: Scored tablets
- Dosing: Single dose
- Price: Approximately $8-$20
- Notes: Pair this with flea treatment to prevent reinfection. If your dog has tapeworms, they almost certainly have (or had) fleas. See our guide on the best flea collars for dogs for prevention.
Best for Roundworms and Hookworms: Durvet Triple Wormer (Pyrantel + Praziquantel)
A solid two-in-one option that covers the most common intestinal parasites including both types of tapeworms.
- Active ingredients: Pyrantel pamoate + praziquantel
- What it treats: Roundworms, hookworms, tapeworms
- What it doesn’t treat: Whipworms, heartworms
- Format: Chewable tablets
- Dosing: Single dose, repeat in 2-3 weeks
- Price: Approximately $10-$25
- Notes: A good middle-ground option when you want broader coverage than pyrantel alone but don’t need whipworm treatment.
Best Monthly All-in-One (Prescription): Interceptor Plus
If you want one product that handles heartworm prevention plus all four major intestinal parasites, Interceptor Plus is the standout.
- Active ingredients: Milbemycin oxime + praziquantel
- What it treats: Heartworm (prevention), roundworms, hookworms, whipworms, tapeworms
- Format: Monthly chewable tablet
- Price: Approximately $50-$100 for a 6-month supply (varies by dog weight)
- Notes: Requires a prescription and a current negative heartworm test. This is the most comprehensive monthly parasite prevention available in terms of intestinal parasite coverage. Discuss with your vet.
Best Combination Coverage (Prescription): Simparica Trio
For owners who want flea, tick, heartworm, and intestinal parasite coverage in a single monthly chewable.
- Active ingredients: Sarolaner + moxidectin + pyrantel pamoate
- What it treats: Fleas, ticks, heartworm (prevention), roundworms, hookworms
- What it doesn’t treat: Whipworms, tapeworms
- Format: Monthly chewable tablet
- Price: Approximately $60-$120 for a 6-month supply
- Notes: Prescription required. Doesn’t cover whipworms or tapeworms, so it’s not a complete intestinal parasite solution, but the combination of flea/tick plus heartworm plus the most common intestinal worms in one product is extremely convenient.
Deworming Schedule: A Year-Round Protocol
Here’s the prevention schedule I follow and recommend, adjusted for different life stages.
Puppies (2 Weeks to 6 Months)
Puppies are born with or quickly acquire roundworms, so early and frequent deworming is critical.
- 2, 4, 6, and 8 weeks of age: Pyrantel pamoate (your breeder or vet should handle the first rounds)
- 8 weeks and beyond: Begin monthly heartworm prevention (prescription required - your vet will start this at the first puppy visit)
- Monthly through 6 months: Continue deworming on your vet’s recommended schedule
Adult Dogs (6 Months to 7 Years)
- Monthly: Year-round heartworm prevention (non-negotiable in most of the U.S.)
- Every 3-6 months: Broad-spectrum intestinal dewormer OR rely on monthly preventatives that include intestinal parasite coverage
- Annually: Fecal test at your regular vet visit to screen for parasites
- As needed: Targeted treatment if you see tapeworm segments or a fecal test comes back positive
Senior Dogs (7+ Years)
Senior dogs have weaker immune systems and are more susceptible to parasite-related complications.
- Monthly: Year-round heartworm prevention (same as adult dogs)
- Every 3-6 months: Broad-spectrum intestinal dewormer
- Twice yearly: Fecal test (semi-annual vet visits for senior dogs should include this)
- As needed: Targeted treatment based on test results
High-Risk Dogs
Dogs that hunt, eat prey, frequent dog parks, live in multi-dog households, or spend time in kennels may need more frequent deworming. Discuss a tailored schedule with your vet.
How to Give Your Dog a Dewormer
Most modern dewormers come in chewable or flavored tablet form, which makes dosing much easier than it used to be. But if your dog is a champion at spitting out pills, here are some strategies:
- Hide it in food: Wrap the tablet in a piece of cheese, lunch meat, or a pill pocket. Give a plain treat first, then the treat with the pill, then another plain treat. The “three treat trick” works because the dog is focused on the next treat, not on inspecting the current one.
- Crush and mix: If the product allows it (check the label), crush the tablet and mix with a small amount of wet food or peanut butter.
- Powder products: Products like Panacur C come as a powder that mixes directly into food, bypassing the pill problem entirely.
- Liquid formulations: Pyrantel pamoate is available in liquid form, which can be easier to dose for small dogs or puppies using a syringe.
Always dose according to your dog’s current weight. Underdosing won’t fully clear the parasites. Check the product label carefully and weigh your dog if you’re unsure.
Signs the Dewormer Is Working
After administering a dewormer, you might see worms in your dog’s stool. This is normal and actually a sign that the medication is working - it’s paralyzing or killing the worms, and your dog’s body is passing them. You might see:
- Live but sluggish worms in the first 24 hours
- Dead worms in stool for 1-3 days after treatment
- Mild, temporary digestive upset (soft stool, decreased appetite) - this is common and usually resolves within 24-48 hours
If your dog has a heavy parasite load, the die-off can cause more noticeable symptoms. Contact your vet if you see vomiting, severe diarrhea, or lethargy lasting more than a day after deworming.
A Note About Heartworm Prevention
I want to emphasize this because it’s the highest-stakes parasite issue your dog faces: heartworm prevention should be year-round and is prescription-only.
Never give a heartworm preventative to a dog that hasn’t been tested for heartworm. If a dog with an active heartworm infection is given a preventative, the sudden die-off of microfilariae (baby heartworms circulating in the blood) can cause a severe, potentially fatal reaction.
Your vet will run a simple blood test before starting heartworm prevention and annually thereafter. The monthly cost of prevention ($5-$15/month) is a fraction of heartworm treatment ($1,000-$3,000+), which also comes with significant health risks for your dog.
For more on all aspects of keeping your dog healthy - from parasites to dental care to preventative routines - visit our Dog Health and Wellness hub.
Frequently Asked Questions
Can I deworm my dog without going to the vet?
For common intestinal parasites (roundworms, hookworms, and tapeworms) in otherwise healthy adult dogs, over-the-counter dewormers are available and effective. However, without a fecal test, you won’t know exactly which parasite you’re treating, which means you might choose the wrong product. For the best results, get a fecal test done so you know what you’re dealing with. And heartworm prevention always requires a vet visit and prescription.
How often should I deworm my dog?
The standard recommendation for adult dogs is broad-spectrum deworming every three to six months, in addition to monthly heartworm prevention. Dogs at higher risk (those that hunt, eat prey, or frequent dog parks) may need more frequent treatment. Puppies need deworming every two weeks starting at two weeks of age until they’re on a regular monthly prevention protocol. Your vet can recommend the best schedule for your specific dog.
Can I get worms from my dog?
Yes, some dog parasites are zoonotic, meaning they can infect humans. Roundworm eggs in contaminated soil can cause visceral larva migrans, particularly in children who play in areas where dogs defecate. Hookworm larvae can penetrate skin, causing cutaneous larva migrans. Good hygiene - washing hands after handling dogs or cleaning up stool, and regular deworming of your dog - significantly reduces the risk.
Why does my dog still have worms after deworming?
Several reasons: the dewormer might not cover the specific type of worm your dog has, the dose might have been too low, or your dog was reinfected from the environment after treatment. Many dewormers kill adult worms but not eggs or larvae, which is why a follow-up dose 2-3 weeks later is often recommended. If worms persist after two rounds of treatment, see your vet for a fecal test and targeted therapy.
Is it normal to see worms after giving a dewormer?
Yes, seeing worms in your dog’s stool after deworming is normal and expected. The medication kills or paralyzes the worms, and your dog’s body expels them. You may see worms for one to three days after treatment. This is a sign the dewormer is working. If you don’t see worms, that’s also fine - some worms are digested before being passed, especially if the infection was mild.