Man feeding dog  chewable tablet for heartworm prevention

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Parasitic worms are a common health issue in dogs because parasites can infect your pooch anywhere, anytime. Dogs can get worms from their mothers, digging in infected soil, sniffing the infected feces of another dog, and mosquitoes. Unfortunately, you can't always prevent parasitic worms, but you can ensure your dog gets the treatment they need to avoid serious health problems. 

A dewormer treats worms in dogs by eliminating parasites, including heartworms. Most young puppies and adopted dogs receive a deworming treatment before entering a new household. It can serve as a preventative measure to ensure a new dog can't infect other pets or people in your home.

This article will discuss everything you need to know about dog dewormers to ensure you understand the process and when to deworm your pet. 

How Dog Dewormers Work

What is deworming for dogs? It's the process of eliminating parasites in a dog. Vets give deworming treatments to dogs as oral medication, an injection, or topical medication to eradicate parasitic worms. Many of these medicines can treat a wide range of parasites.

Some dewormers paralyze worms in the GI system and allow the dog to eliminate them in feces. Meanwhile, other types of medication starve and kill the parasite, preventing it from being able to reinfect another dog once expelled. 

List of parasites dewormers in dogs treat

Treating worms in dogs is crucial because they can cause serious health problems when left untreated and infect other dogs since yours will shed them in their feces. Several types of worms affect dogs, with symptoms ranging from vomiting, diarrhea, and bad gas to blood in stool, blockages, and pneumonia. This includes:

  • Roundworms: Roundworms are transmitted in several ways, including via the placenta from mothers to puppies. 
  • Hookworms: Hookworms are small parasites that burrow into the intestinal wall and feed off your dog’s blood. These worms live in soil, so many dogs get them from sniffing around or eating infected soil outside, and the larvae can either be ingested or burrow through the skin. 
  • Tapeworms: Tapeworms are transmitted through infected fleas that eat tapeworm eggs. The eggs hatch and attach to the intestinal lining. Tapeworms can cause itching around the anus, so it may cause scooting in dogs.1
  • Whipworms: Whipworms are large enough that you might be able to see them in soil. They embed themselves in the intestinal lining and can cause discomfort and unpleasant symptoms in dogs, such as canine diarrhea, weight loss, bloody stools, anemia, and dehydration.
  • Heartworms: Heartworm is another type of worm that is common in dogs. However, it's not an intestinal parasite like the others and can cause serious health problems, eventually becoming fatal if left untreated. Heartworms are spread through mosquitoes and live in infected animals' hearts, lungs, and blood vessels.2 

When To Deworm Your Dog

Knowing the symptoms can help you understand when to take your dog to the vet for treatment. While there are several types of intestinal worms, they can vary. Therefore, your dog may have only a few symptoms on this list:

  • Diarrhea
  • Abdominal pain
  • Vomiting
  • Weight loss
  • Dull coat
  • Bloating
  • Dehydration
  • Lethargy
  • Anemia
  • Intestinal blockage
  • Pneumonia
  • Blood in stool

Again, heartworms are not intestinal worms and have different symptoms that cause coughing, exercise reluctance or intolerance, fatigue, decreased appetite, weight loss, heart failure, and abdominal swelling.2 Because heartworm disease can be fatal, you should have your dog tested once a year and give them preventative medication. 

Puppy deworming schedule

Puppies are highly susceptible to worms because they can get them from their mothers and still have developing immune systems. Therefore, most puppies are first dewormed at two, four, six, and eight weeks of age. They should also receive monthly heartworm prevention for the rest of their lives, which may protect them against other parasites. 

Puppies will receive another treatment monthly from three to six months old. Then, when they become adults, they'll have annual or biannual stool tests at the vet to test for worms and provide treatment on an as-needed basis. That said, the preventative heartworm medication they receive should protect against other types of worms, including hookworms and roundworms. 

Cost Of Deworming

In general, deworming treatments can cost anywhere between $15 to $200. But how much you pay for dog dewormer varies depending on your vet, location, and the type of medication your dog receives. However, you can expect to pay for a vet visit, fecal exam, and deworming medication. In addition, depending on the severity of your dog's infection, they may have to be hospitalized, which can cost thousands of dollars. 

Deworming treatments can cost anywhere between $15 to $200

Heartworm treatment is more expensive because your vet must perform blood work and take x-rays to determine the severity of an infection. The tests can cost a few hundred dollars. Meanwhile, the types of treatment will be costly. Depending on your dog's condition, your vet may use several treatments, including injections and oral medication. Additionally, your dog will need regular follow-ups.

Types Of Dewormers

Types of dewormers for dogs

The type of dewormer your dog needs will depend on the kind of parasite they have. For example, heartworm treatments vary significantly from dewormers for intestinal parasites. Your vet may suggest oral, injectable, or topical treatments. In most cases, oral treatments are the easiest for dogs to ingest. However, injectable dewormers are faster-acting because they only require one dose. 

In any case, your vet will ensure you understand your options and help you determine the best course of treatment depending on your dog, parasite type, and overall needs. 

Dewormer Side Effects

Dog dewormers are considered safe for most dogs, and depending on the type of worm, pet parents may see them in their dog's feces. However, they can have side effects, and dogs with a large number of parasites can experience anemia or other signs of illness after treatment, including the following:

  • Loss of appetite
  • Vomiting & diarrhea
  • Lethargy

It's important to monitor your pet after deworming. In most cases, dogs don't experience any side effects. However, if your dog's behavior changes, they seem more tired, or they have GI upset in the form of vomiting or diarrhea, contact your vet as soon as possible. 

While intestinal pet dewormers for dogs are safe and have minimal side effects, heartworm treatment is very different. With heartworm disease, dogs are given an injectable treatment to kill the adults in the heart, lungs, and blood vessels. Dogs with diagnosed heartworm disease will need a series of injections with a schedule that varies depending on the severity of the infection over the next three to six months. A vet also uses medication to reduce the chances of unwanted side effects. 

While a dog is treated for heartworm, pet parents must restrict exercise because it can increase damage to the heart and lungs.3 Most vets recommend keeping your dog in a bedroom and only letting them outside on a leash to keep them from getting too rambunctious. 

Side effects are more common and severe with heartworm treatment than intestinal parasites. Dogs may experience swelling and soreness at the injection site. Additionally, the more worms a dog has, the more risk there is with treatment. Severe side effects of heartworm treatment include:

  • Worsened cough
  • Difficulty breathing & excessive panting
  • Weakness and lethargy
  • Lack of appetite
  • Diarrhea

Preventing Worms In Dogs

While parasitic worms live in your dog's environment, including the dirt, there are several ways you can protect your pet from uncomfortable and potentially fatal complications. The best way to treat worms in dogs is to prevent infections from occurring in the first place. Here are a few ways you can prevent worms in dogs:

  • Eliminate fleas: Since fleas can carry tapeworms, you should protect your pet year-round by investing in flea prevention products. You can find collars, topical, and oral medications to get rid of fleas, which will reduce the likelihood of tapeworms. 
  • Use heartworm prevention: Heartworm prevention doesn't just protect your dog from heartworms. Many products are broad-spectrum and can protect them against intestinal worms also. 

African-American male vet petting cute dog on woman's lap

  • Visit your vet: Your dog should have an annual or bi-annual wellness visit that allows your vet to perform a fecal exam to test for signs of worms. Additionally, your vet will perform a blood test to check for heartworm. These exams are crucial because they allow your vet to catch signs of illness before they cause health complications. Additionally, the earlier you treat worms, the better your dog's prognosis.
  • Pick up pet poop: Picking up your dog's poop while on walks can prevent it from infecting other dogs that pass by. Additionally, never let your dog sniff another dog's droppings on walks because it can transmit worms to them. 

Dog Dewormer: FAQs

Which dewormer is best for dogs?

There are many different options for dog dewormers. However, what's best for your dog depends on the type of worms they have or the worms you're trying to prevent. If you need help deciding which medication to use for your dog, consult your vet. They can discuss brand options and provide you with resources to learn more about parasite prevention to protect your pooch. 

How often should dogs be dewormed?

How often dogs should be dewormed depends on their age and lifestyle. Puppies will receive regular deworming treatments as soon as they turn two weeks old. Additionally, some experts believe you should treat your dog for worms every three months, depending on their lifestyle.4 However, you can (and should) use a monthly preventative dewormer for dogs, which can protect against heartworms, fleas, and intestinal parasites. 

How do I know when to deworm my dog?

Every dog needs a yearly physical examination by a vet, who will ask you to bring in a fecal sample for testing. Some vets do fecal testing on-site, while others send it to a lab. In any case, you'll get the results back quickly, which will tell you and your vet if your dog's stool has signs of worms. If your dog's stool returns healthy, no treatment is needed other than your monthly prevention plan. However, if your dog's stool shows signs of worms, your vet will want to begin treatment as soon as possible. 

Final Notes

Deworming dogs is crucial because parasites can cause significant suffering and be fatal. Additionally, some parasitic worms can spread to humans, infecting the entire family and other pets in the household. Since worms cause unpleasant side effects, a dewormer for dogs is the best course of action after diagnosis. 

Of course, prevention is key to ensuring your dog lives a happy, healthy life. Talk to an online vet today to learn about your deworming options and find the right preventative medicine to protect them year-round.



  1. Nelson, Jennifer. "Why Is My Dog Scooting?" American Kennel Club, 15 Sept. 2022,

  2. "The Facts about Heartworm Disease." U.S. Food and Drug Administration, FDA,

  3. "Heartworm in Dogs." American Heartworm Society, 24 Jan. 1970,

  4. "Worms." The Kennel Club,

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