Written by Vet Evidence Based

Deworming Dogs And Puppies: Everything You Need To Know

Margarita Boyd
Written by: Dr. Margarita Boyd, BVSc MRCVS
Use this deworming guide to discover the best practice for treating roundworms, hookworms, and other parasites.

The thought of your dog having worms might make you squirm, but its important to be knowledgeable about this common canine problem.

Every dog is as at risk of worms and deworming your pooch plays an important role in keeping your dog happy and healthy.

There are many different types of worms that can infect your dog, and they can cause a variety of problems from tummy upsets and weight loss to coughing or even heart failure!

Some canine worms can even infect and cause health problems in people, so it’s important to protect you and your family too.

In this article, we will take a look at why it’s important to deworm your dog or puppy, as well as what type of worms can infect dogs and how they can be treated.

We will also look at how often your canine pal should be dewormed to keep him parasite free!

Why Deworm Your Dog?

Parasitic worms can cause a lot of problems for your dog. Here are the main reasons why regular deworming is important:

1. Dogs Don’t Always Show Obvious Signs Of Worms

Sometimes dogs can have a lot of worms in their intestines, lungs or heart, and not show any outward signs of infestation until its too late.

They might appear healthy on the outside, but the worms will probably be causing damage on the inside.

For example, lungworm can cause blood clotting problems, which can lead to the dog suddenly having a serious internal bleed.

2. Health Risk For Humans

A common dog worm, Toxocara Canis, can infect and cause problems in humans. (1)

Children are at a higher risk of infection, and the larvae (young adult worms) can travel to the brain or eye and cause problems such as seizures or blindness. Therefore, regular deworming of family pets is extra important!

3. Prevention Is Better Than Cure

Worms can cause some serious health problems for your pooch. Puppies pick up worms from their mum through the placenta, and then once they are born through the milk.

They require extra deworming as high worm burdens in puppies can cause tummy upsets, intestinal blockages or even stunted growth. In adult dogs regular deworming helps to prevent infections, so your dog doesn’t develop any serious consequences of worm infections.

What Types Of Worms Can Infect Your Dog?

There are many different types of parasites that can infect dogs, with some types of worms causing more serious problems than others.

The type of worms that your dog is at risk of being infected with depends on where you live, your dog’s lifestyle, if he hunts or eats small prey or if you travel abroad with your pooch.

Your veterinarian will be able to tell you which parasites your dog is at risk of contracting.

Let’s take a look at the most common canine worms:


Roundworms (Toxocara Canis) are long, white worms that look like spaghetti.

These worms are very common and live in the dog’s intestines. Most puppies are born with a roundworm infection, as the worms pass through the placenta before the pup is born or through the mum’s milk after the pups are born.

Dogs can also get infected with roundworms by eating poop, dirt or small prey infected with roundworm eggs. (2)

Clinical signs: Classic pot belly appearance in puppies, diarrhea, vomiting, weight loss, stunted growth, dull coat or intestinal obstruction. Roundworms can appear in other animals, including cats.

Roundworms in humans: If a healthy adult human accidentally ingests roundworm eggs, then the infection usually causes no problems. However, the risk is greater for children that become infected with roundworm eggs, as they can cause signs such as seizures or blindness!


Hookworms (Ancylostoma caninum, Ancylostoma braziliense) are a common type of intestinal parasite in dogs.

These small tough worms are mini vampires, sucking the dog’s blood as a way to survive. Adults get infected from eating infected poop or soil.

Puppies can become infected from their mum’s milk if she has a hookworm infection.

Clinical signs: Mild diarrhea, weight loss or anemia (pale mucus membranes, weakness).


Tapeworms (Dipylidium caninum, Echinococcus multilocularis) are long, flat parasites that attach to the lining of the dog’s intestines. These worms are spread by fleas. Dogs become infected by eating fleas that contain the tapeworm egg.

Clinical signs: In adult dogs, a tapeworm infection doesn’t normally cause many symptoms apart from finding small, “rice-like” segments in the dog’s poop.

A tapeworm infection can be more serious for puppies causing signs such as stunted growth, poor health or anemia. (3)


Whipworms (Trichuris vulpis) are a common intestinal parasite, that live in the dog’s large intestine. These nasty little worms measure about a ¼ inch long and suck the dog’s blood to survive. Dogs become infected with whipworms from eating infected poop or soil.

Clinical signs: Bloody diarrhea, weight loss, weakness or anemia.


A few different worms can cause a lungworm infection in dogs. Which one your dog is at risk of developing, depends on where you live.

In Europe, canine lungworm infection is mainly caused by Angiostrongylus vasorum, while in North America it could eucoleus aerophilus, Oslerus osleri or Crenostoma vulpis. (3)

Dogs become infected by swallowing the immature worm, where it then travels through the dog’s body and settles in the lungs to cause problems for the dog.

Clinical signs: A dog with lungworm infection may have no symptoms at all or can develop a serious, life-threatening condition with signs such as increased breathing rate, weakness, coughing, sneezing, nose bleeds, internal bleeding or collapse.


Heartworm infection is caused by the parasite Dirofilaria immitis, which is spread by mosquitoes. Adult heartworms can measure up to 36cm long, and live in the heart and nearby blood vessels, where they can cause significant problems for the dog.

On average an infected dog has around 15 heartworms, but some infected dogs might have up to 300 of these worms living in its heart!

Clinical signs: Coughing, reluctance to exercise, weakness, fainting episodes, weight loss, ascites (tummy filled with fluid) or collapse.

What To Do If You Think Your Dog Has Worms?

Ideally, you should go to your veterinarian if you think your dog has worms and is showing signs of sickness. It’s a good idea to bring a fresh sample of your dog’s poop too, just in case they want to run some tests.

Your veterinarian will be able to prescribe a safe and effective deworming treatment for your dog’s age and weight.

How Are Worm Infections Diagnosed?

Often a veterinarian will suspect that your dog has a worm infection just from his symptoms, clinical history and/or physical examination.

Sometimes its easier to treat the suspected parasitic infection, rather than doing furthermore expensive diagnostic tests.

However, sometimes further tests are necessary. Diagnostic tests vary depending on the type and lifecycle of the worm.

  • Intestinal worms can often be diagnosed from a simple poop/fecal sample. A laboratory test called a fecal flotation can be done to analyze the sample under a microscope and look for worm eggs.
  • Lungworm can be a little more difficult to diagnose. Some types of lungworms can be diagnosed from a simple blood test, others may require a poop sample, x-rays, or bronchoscopy (looking inside the lungs with a tiny camera).
  • Heartworm is usually diagnosed by a simple blood test. However, further tests may be needed including x-rays and echocardiography (ultrasound of the heart).

How Often Should You Deworm Your Puppy?

The following worming recommendations are from the European Scientific Counsel Companion Animal Parasites (ESCCAP):

Puppies should be dewormed:

  • From 2 weeks of age, every 2 weeks until 10-12 weeks of age
  • Then every month until 6 months of age

All puppies are born with worms, as they pass through the placenta before they are born and through the mum’s milk after birth too.

Young pups have an immature immune system which means they can struggle to fight off infections. (4)

In puppies, intestinal parasites can cause tummy upsets (vomiting, diarrhea, nausea), poor growth, anemia or even intestinal blockages.

This is why it is recommended that puppies are dewormed much more frequently than adult dogs. After 6 months of age then can move onto an adult deworming schedule recommended by your vet.

How Often Should You Deworm Your Adult Dog?

How often you need to deworm your dog depends on its age, it’s a lifestyle and what worms it is at risk of catching. There is no easy answer that is suitable for every dog, and you should work with your vet to figure out what is best for your dog.

If you travel abroad or to a new area you might need to adjust your worming protocol. Let’s look at the most common options:

1. Deworming Every Month

If your dog hunts, eats prey or eats other dog’s poop then it is at higher risk of intestinal worms and needs more frequent deworming.

If you live in an area that is at risk of lungworm or heartworm infection, then your dog will need a preventative treatment against these worms every month.

Many veterinarians recommend that your adult dog receives a monthly deworming treatment.

A monthly deworming treatment stops your dog from developing a worm infection and excreting potentially harmful worm eggs, especially if your:

  • Dog lives with young children or an immunocompromised person
  • Dog eats prey or goes out hunting
  • Dog eats other dog’s poop
  • To protect your dog against heartworm
  • To protect your dog against lungworm

2. Deworming Every 3 Months

If you don’t want to deworm your dog that often, then you need to talk to your veterinarian and take steps to prevent your dog from getting infected.

Dogs should be dewormed at least 4 times per year(every 3months) to protect them against intestinal parasites, and reduce the number of worm eggs (which are potentially harmful to humans!) they produce in their poop.

Studies have shown that giving a dog a deworming treatment only 1–3 times a year does not provide sufficient protection! (5)

What Deworming Products Should You Use?

There are so many different deworming products available that it can get confusing about which one is best for your dog. You might want a tablet, an easy to give paste or solution or find that a liquid spot-on or collar is best for your pet.

However, did you know that some deworming products that are sold online, in supermarkets or in pet shops might not be safe for your pet?Also many “natural” dewormers are not very effective at all!

Some deworming ingredients given to adult dogs might not be safe for your puppy, or your pregnant pooch. Your veterinarian can help you choose one which is safe and effective for your dog. (6)

Which wormer to give your dog depends on which worms you want to treat or protect him against. Additionally, each country will have their own veterinary licensed products.

Your veterinarian will help you decide on an individual plan, especially for your dog.

Common Deworming Products For Dogs

Let’s look at some common deworming products for dogs and their active ingredients:

Panacur is a commonly used dewormer for puppies. It is an easy to administer solution or paste which contains the active ingredient fenbendazole. Your pup needs to be accurately weighed to calculate his dose.

MilbeGuard contains the active ingredient milbemycin oxime and is a once-a-month flavored tablet for dogs and puppies (from 4 weeks of age).

This wormer prevents heartworm disease, controls hookworms and removes and controls roundworms and whipworms.

Milbemax is another common all in one deworming medication, it contains the active ingredients milbemycin oxime and praziquantel.

It can be used to treat and prevent hookworm, roundworm, whipworm and tapeworm infections. It can also be used to prevent heartworm and lungworm infection in dogs if used monthly.

Tri-Heart Pluscontain the active ingredients ivermectin and pyrantel.

These chewable tablets can be used for the control and treatment of roundworms and hookworms and the prevention of heartworm in dogs.

Drontal Plus uses the active ingredients praziquantel, pyrantel, and febantel which offers broad-spectrum activity against hookworms, roundworms, tapeworms, and whipworms.

It’s easy to give a flavored tablet that can be used on puppies at least 3 weeks of age.

How Much Dewormer Should You Give Your Dog?

Every veterinary licensed deworming product should have dosing guidelines on the packaging. If you buy a licensed product you know it is safe and regulated.

The dose of dewormer usually depends on the weight of your dog or puppy. That means you need to accurately weigh your dog, to find out how much medication he needs.

If you guess your dog’s weight, you could end up giving him too much (and risk overdosing!) or giving too little (and it won’t work!).

It is extra important to carefully weigh puppies and give them an accurate dose of dewormer that is safe and suitable for pups.

Can Worm Infections Be Prevented?

The good news is that there are some easy ways for you to help prevent your dog from picking up worm infections.

A regular deworming schedule is important but so are taking steps to keep your dog from being re-infected from his environment, including:

  • Promptly picking up dog poop
  • Keep your garden clean from dog poop
  • Wash your hands after you have handled dog poop
  • Wash your hands after touching your dog (especially children)
  • Keep your dog (and any cats in the home) flea-free, as they transmit tapeworms
  • Prevent your dog from eating unknown things on walks (other dog’s poop, rubbish, etc.)
  • Prevent your dog from hunting or eating prey
  • Prevent your dog from eating snails (certain lungworm infections)


Regularly deworming your dog or puppy is part of being a responsible dog owner. It helps keep your dog healthy, happy and worm free!

There are lots of different canine worms that can infect your dog’s intestines, heart or lungs, and can cause some serious consequences for your pooch (and infect humans too!).

Puppies are at higher risk of becoming ill with worm infections, that’s why they need to worm frequently in the first few months. Thankfully there are lots of safe and effective worm treatments that you can use to treat and prevent worms.

The best place to get a dewormer is from your veterinarian, who can make a tailored plan that suits your pet.