How do Dewormers Work in Dogs? Everything You Need to Know

Deworming a dog is just one of our responsibilities as pet owners. It ensures that our pooches are safe from life-threatening parasites. But have you ever wondered: how do dewormers work in dogs? For this post, we discuss how deworming works, mistakes you need to avoid, deworming schedule, and other things you need to know.

Why is dog deworming necessary?

Dog deworming has one goal: to keep parasites off your dog. Aside from keeping the nasty worms, there are more benefits to deworming than you think:

*It will prevent intestinal problems

The leading problem that worms bring is diarrhea and stomach pain. The parasites feed on the walls of the intestines, which causes pain and discomfort. It will also trigger vomiting, which may dehydrate your dog. Over time, your pooch will also have a poor appetite, experience weight loss, and experience weakness.

*It will save your dog from heart problems

This may sound surprising, but yes, worms can be spread through the bloodstream and reach the heart. Once your dog acquires heartworm, it will start to grow and spread. Over time, it will lead to heart failure, lung problems, and other complications on other internal organs. If not removed, heartworms can grow into pasta-like lengths, which can block arteries and circulation.

*It will prevent anemia

Worms feed on your dogs’ blood and nutrition. Once the worms reproduce and spread, they will consume more blood, which will lead to anemia. If not addressed right away, anemia will branch into other problems.

*It will save other dogs

Aside from curing your dog, you will also save other canines from infestation during deworming. This is crucial, especially if you have a multi-dog household. Dogs that share beds, food, and toys are at great risk of spreading worms.

Here’s why you should deworm your dog regularly courtesy of

Types of worms that may infest your dog

Worms aren’t a single problem. Your dog may contract various types of worms at a time, which will cause severe symptoms. You should be aware of the following worms that may infect your pooch:


Roundworms are one of the most common parasites among canines. These worms harbor on your doggos’ intestines where it feeds and reproduces. Also called ascarids, roundworms look like thin spaghetti pasta that are a few inches long. It also has a light brown or whitish color that can be expelled on your dog’s vomit or poo.

Moreover, dogs with roundworms will have ‘pot-belly’ due to the proliferation of the worms in the intestines. Also, your dog will experience diarrhea, vomiting, belly pain, and weakness. Over time, roundworms will also cause a dull coat due to anemia and the nutrition it steals from your pet.

Take note that dogs can acquire roundworms from their mothers during lactation. Also, it can be passed before birth or through the environment. Your dog can also get it from other dogs.

It’s essential to diagnose a dog with roundworms to give it the proper cure. Veterinarians will usually administer deworming drugs like moxidectin, fenbendazole, pyrantel, piperazine, and milbemycin. As much as you can deworm your dog at home, it’s best to consult a vet for safer deworming.


Unlike roundworms, tapeworms are flat and segmented. Your dog can acquire different sub-types of tapeworms, and each one needs to be treated right away.

If placed under a microscope, you’ll see that tapeworms bear a hook-like mouth structure. If it grows, it can be as long as 11 inches. Take note that tapeworms can spread through proglottids are the broken segments usually found on canine excreta. Each proglottid carries up to 20 eggs that will hatch inside your dogs’ stomach.

Your dog can also acquire tapeworm when it ingests flea infected with tapeworm larva. Unlike roundworms, your dog won’t acquire tapeworms if they eat fertilized eggs. It needs an intermediate host first before it can infect your pooch.

Usually, tapeworms don’t pose serious health problems. Still, it will irritate your dog, which will cause them to drag their bottoms to the ground.

However, if puppies got infested by a tapeworm, you should seek the help of a veterinarian. The proliferation of tapeworms in puppies may cause intestinal blockage, anemia, and stunted growth.

To cure tapeworms among dogs, vets may inject or administer tablet drugs to expel the worms.


Coccidia isn’t necessarily a worm, but it can also be removed through deworming. These are single-celled parasites that will live in your dog’s intestines. Puppies are the common hosts, but cats and dogs can also acquire it through the ingestion of infected soil and dog feces.

Some dogs with coccidian won’t necessarily experience adverse symptoms. The most common is diarrhea and bleeding. Most adult dogs can survive this infection, but puppies have a higher risk of infection.

The good thing about coccidian is it can’t be transferred from dogs to cats and vice versa. Still, you should consult your dog’s veterinarian to get it removed.


Like roundworms, whipworms are intestinal parasites that thrive in the cecum of your dog’s large intestine. When your pet gets infested with whipworm, it will experience watery or bloody diarrhea, weakness, weight loss, and severe discomfort. Take note that of all the parasites that can harbor in your dog’s stomach, whipworms bring the most diseases.

These worms are 6 mm long and can be passed on through the stool of infected canines. Take note that the eggs of this worm can be microscopic and will need the help of a veterinarian for proper diagnosis.

Several drugs can be administered to cure whipworm. However, it will take two doses to remove whipworms from your pet thoroughly. Also, dogs that have infected with whipworms have a high rate of re-infection, so re-treatment is also necessary every three to four months.

Nevertheless, whipworms aren’t as common as roundworms nowadays due to various heartworm products available for pet care.


Ringworms are infamous among humans due to the red, rounded, and raised skin infections it causes. Actually, ringworms can be due to a variety of pathogens and fungus. Nevertheless, about 70% of all ringworm cases nowadays are due to Microsporum canis.

Once your dog gets infested with ringworms, the parasite will grow on the outermost layer of your pooch’s skin. So unlike other worm infections, ringworms are superficial and will target the hair follicles of your dog. Also, the infection will be in patches and can cause bald spots among canines.

Take note that your dog will acquire ringworm through direct contact with the fungus. So if your dog licks a contaminated comb, couch, carpet, or food bowl, there’s a chance that it will become a host. You should know that ringworm fungus spores can remain infectious for up to 18 months and can be spread through shed fur.

If your dog suddenly exhibits brittle hair, hair loss in circular areas, brittle claws, and flaky skin, you should get it tested for ringworms. Over time, ringworms will impact the quality of life of your dog. It’s best to have it treated on the first sign of infection.


Hookworms are similar to roundworms and tapeworms since it also lives in the intestines of your pooch. Once it enters your dog’s intestines, it will attach itself to the lining of the digestive system, where it will feed and reproduce. In the process, the hookworm will eject eggs into the digestive tract. So when your dog eliminates, it will also expel the eggs, which may potentially infect other canines.

The alarming fact about hookworms is it can infect your dog through skin penetration and routine licking.

Usually, hookworms may cause vomiting and diarrhea. However, it can be lethal for puppies. Since these little pooches have a small body size, they are prone to anemia and internal blood loss. During the worst infestations, the dog may need transfusions to survive. This is why it’s essential to call a veterinarian once you notice signs of worm infestation on your pet. Regular deworming can prevent any complications.


Heartworm in dogs is probably one of the most dangerous parasites your dog may get. This blood-borne parasite lives in the heart. Also, it can grow for up to 14 inches long, which will block the arteries and lead to heart failure.

The frightening thing about heartworm is it can spread in the pulmonary artery, heart, large blood vessels, and other adjacent areas. In worse cases, the worms could even be swimming in your dog’s blood.

Moreover, heartworms need an intermediate host to infect your dog. The most common are mosquitoes. In fact, there are over 30 mosquito species that can transmit heartworm to canines.

However, the consolation here is that heartworm won’t spread from dog to dog. But since it’s a life-threatening parasite, you should always seek immediate treatment.

Heartworm can take months to mature inside your dog’s heart; that’s why it’s not usual to observe symptoms among puppies. However, when the dog exhibits adverse heartworm symptoms, the parasite has already spread all over its body. It will cause clogging and poor circulation that can lead to the death of a dog.

If your dog has an advanced heartworm infection, surgery might be needed to extract the worms out. Nevertheless, some dogs can be treated with various drugs. It’s essential to have your dog treated right away as heartworm can also cause damages to the liver, lungs, and kidney.

Where do these worms come from?

Worms can come from a variety of sources, depending on the type that infests your dog. Most intestinal worms can be acquired through the ingestion of an infected matter. It could be soil, the poop of an infected dog, fungus, and so on.

Also, it can be through an intermediate host like an infected flea or mosquito. Also, some worms can penetrate your dog’s body by piercing through the skin, mostly on the feet area. And if your dog happens to have wounds, infections can easily take place.

So even if your dog doesn’t play outdoors, there’s still a chance that it will become infected with worms.

The takeaway: deworming is crucial across all breeds.

Signs that your dog has worms

There are general signs that you have to watch out for which indicates that your dog has worms. If you notice the following on your pooch, make sure that you bring it to the vet right away:

-Diarrhea (even so if bloody)
-Intense coughing
-Weakness and lethargy
-Unexplained weight loss
-Poor appetite
-Pot belly or long periods of bloating
-Dull coat or bald spots in circles
-Scooting or rubbing its bottom on the floor
-Rice grain-like substance near the anus

If you notice that your dog experiences some of these symptoms, it’s best to seek professional help. Your dog will be given a general check-up first before the veterinarian administers a deworming drug. If your dog has an extreme weakness, avoid deworming it on your own. Dehydration may set in, which may put your dog’s life at risk.

Also, some signs of worms can overlap with other conditions. This is why proper diagnosis is necessary.

In this video, MyPet tells us more about the signs of worm infestation in dogs:

Common deworming drugs

Veterinarians use a variety of deworming drugs, depending on the kind of worm present in your dog’s body. Also, they have to consider the health condition of your pooch as well as its age. But basically, the following drugs can be used.

NOTE: Only a licensed veterinarian should administer any deworming drug unless the latter gives you a go signal for home use.


This drug is used for two types of roundworms and must be administered twice to kill the worms totally. Moreover, it should be given at least 10 days apart to prevent any harsh side effects.

*Pyrantel Pamoate

This is considered a safe deworming agent for roundworms, pinworms, hookworms, and other worms in dogs. It will paralyze the worms so they will release their grip on the doggo’s digestive tract. From there, it will be expelled through elimination. Just make sure that you clean up after your dog to prevent the spread of the potentially surviving eggs. It has to be administered twice or thrice with a two to four-week gap.


This is actually a preventative deworming agent against heartworms for both cats and dogs. Aside from that, this drug also works for ear mites, lice, and mange. However, it only works for the parasites your dog has been exposed to in the preceding month.

Upon giving Ivermectin to your dog, the drug will interrupt the nervous system of the heartworm larva.


This dewormer covers a wide range of worms for small to large animals. When used in dogs, it’s effective in dispelling whipworms, hookworms, and roundworms. It can also remove giardia from your pet. 

Your dog’s vet may use other anthelmintic drugs. You must seek the advice of a vet to ensure that the deworming process is safe and suitable for your pet.

How the deworming process works

The deworming process starts by confirming the presence of the parasite and what kind is harboring on your dog’s body. Once the veterinarian determines the type of parasite and extent of the infestation, it will prepare the deworming drug that suits your pooch.

Usually, the vet will conduct stool and blood testing to spot the worms. This way, the vet can determine the type of worm or if your dog is experiencing adverse symptoms like anemia.

Take note that each dog requires a personalized dosage and deworming process. Canines with lingering illnesses need intensive care and attention to ensure that the deworming process will not endanger their life.

Nevertheless, some vets may recommend an over-the-counter dewormer after the initial treatment at the clinic. Always follow the dosage and instructions to prevent any untoward incident.

Take note that deworming a puppy is different from deworming an adult or senior dog.

In this video, Royal Kennels shows us how to deworm a puppy on your own:

How much does dog deworming cost?

Depending on the extent of the infestation and needed dosage, a deworming session may cost anything between $40 and $80. In some instances, it could be higher or lower. If the vet gives the green light for home deworming, you can save a larger amount.

OTC dewormers are available for $20. However, you’d still have to pay for the fecal and blood test before the deworming session. Anyway, you can find clinics that offer affordable testing. Some shelters and city animal offices may offer free testing as well.

Dog deworming schedule

Dogs have varying deworming schedules based on their age. If you’re at a loss, it’s best to ask a veterinarian about it. Some of the deworming shots can be given to puppies in a 3-way or 4-way method together with other core vaccinations.

The American Association of Veterinary Parasitologists (AAVP) recommends a strategic deworming process to ensure that your dog is protected all year long. In the same vein, the Centers for Disease Control and Prevention (CDC) also have their own guidelines.

Basically, deworming schedules for dogs are as follows:

*Puppies (also applies to kittens)

Puppies are very vulnerable to worm infections. And with their small bodies, they are also prone to the adverse effects of the parasites. This is why it’s essential to know when the right time is to deworm your pooch.

First deworming: ages 2, 4, 6, and 8 weeks.
Second deworming: ages 12 and 16 weeks
Succeeding deworming: re-treatment at 6 months or 1 year of age

Many vet clinics will offer this in package pricing, so you no longer have to look for another clinic for the series of deworming.

*Adults (applies to adult cats as well)

General deworming: twice a year (for life)
Dogs that stay inside most of the time: once a year
Hunter and outdoor dogs: two to three times a year based on vet’s advice.

Take note that adult dogs can be very adventurous, and they put everything on their mouths. Also, if you have an aggressive chewer, you may need to deworm them more often than other canines.

Nevertheless, you should always ask the help of a veterinarian to know if it’s the right time to deworm your dog or not. Also, if your dog exhibits adverse reactions to deworming, you should bring it to a vet in the soonest possible time.

*Newly adopted or owned dogs (cats as well)

First deworming: immediately after getting the animal
Second deworming: two weeks after the first deworming
Third deworming: apply the puppy and adult deworming schedule above

Before you deworm your dog…

Before you try deworming your dog, make sure that it’s in good shape. If your dog looks weak and sick before deworming, it’s best to have it checked by a vet first. Your pet might have underlying illnesses that could put its life in danger if you deworm.

Traveling with your dog? Special deworming might be needed

If this is your first time traveling with your dog overseas, you should know that heartworm is everywhere. Aside from that, many airlines and pet couriers require a specific set of vaccinations and treatments be done to your dog before transport. This way, your pet will not spread any disease to other dogs and the place where you’re headed.

Do dog worms pose harm to humans?

The answer is yes. Many worms that dogs get can be transferred to humans. As with dogs, parasitic worms can cause a myriad of problems to humans, especially children. Heartworm, roundworm, and ringworm can be transferred to humans and have the same effect as it does with canines.

Since kids put a lot of things in their mouths, they are at great risk of contracting worms. This is much true if you have an infected dog at home, and you let your child mingle with it.

If a child or adult ingests worm eggs, it can thrive inside the body and reproduce at exponential rates. Like dogs, adults with severe worm infestations can develop potbelly and a myriad of other complications.

Take note that when worms get into the brain or eyes, it can cause serious consequences like blindness or seizures. This is riskier for children.

So aside from keeping your pet healthy, deworming is also necessary to guard your family as well.

how do dewormers work in dogs

Mistakes you need to avoid

Take note that deworming isn’t a one-shot deal. In most instances, second or third deworming is necessary to remove all the parasitic worms in your dog’s body. Also, you must avoid the following mistakes that many dog owners tend to commit:

*Not factoring in your dog’s weight

Like what we mentioned earlier, each dog requires a specific deworming process. Take note that checking your dog’s weight is critical when deworming so you can give it the right dosage. A lower dosage than necessary will not remove the worms successfully. However, a higher dose can be lethal, especially for puppies.

If you can’t weigh your dog for some reason, it’s best to ask a vet about anthelminthic drugs with a wide weight range classification. This way, you can limit the risk.

*Not performing follow-up deworming

After the initial deworming of your dog, it’s critical to perform follow-up deworming based on the schedule we discussed above. This is to guarantee that the worms will be eradicated fully.

Take note that most deworming drugs should be re-administered two weeks after the first one. The only exception here is if your dog received a sustained-release drug that will be effective up to a month.

 *Not personalizing your dog’s deworming schedule

 Each dog requires a specific deworming schedule depending on its activity, age, weight, and health conditions. As much as the CDC and AAVP recommend specific guidelines, it’s always best to consult with your dog’s vet. This way, the vet can advise you of the right dosage and schedule.

*Not checking if an oral dewormer has been swallowed

Dogs don’t like any nasty tasting food. So if you administer an oral dewormer, make sure that it’s swallowed properly. Always observe your dog for a few minutes after giving the dewormer. This way, you can check if the pooch will spit out the drug.

If your pooch has a hate-hate relationship with oral dewormers, you might as well look for injectable or skin-absorbed types. This ensures excellent absorption and efficiency.

*Deworming your dog on your own

We can’t emphasize this enough: never deworm your dog on your own. Always seek the assistance of a veterinarian so your dog will be checked prior to deworming. This is very crucial as some dogs turn out unfit for immediate deworming.

Buying an OTC dewormer and giving it to your dog haphazardly is a recipe for disaster. It may do more harm than help, no matter how good your intentions are.

*Thinking that a single dewormer can solve all parasite problems

Newbie dog owners often think that a single dewormer can fix all the parasite problems of their pets. However, you should know that each one has specific active ingredients that target specific types of worms.

Why don’t they make one with all the needed dewormers? Well, if that’s the case, such dewormer would be lethal for dogs. It’s like throwing a grenade into your dog’s stomach. The master dewormer will attack all types of worms, which will cause adverse effects on the canine.

So before you purchase an OTC dewormer, bring your dog to the vet. The animal doctor will run blood and stool tests to determine the type and species that infest your pooch.

Safety tips when deworming a dog

How do dewormers work in dogs? The vet can advise you on this matter. So if your dog is due for deworming, always keep the following safety tips in mind

-Trust the vet

The vet is the best person to ask about the condition of your dog. Veterinarians are also the people who can advise you about proper deworming and what your dog needs. So if the vet prescribes a specific deworming drug and instructions, always follow it religiously.

-Always check what you give your dog

So you purchased a dewormer, and you gave it to your dog. Did you even read the label and its active ingredient? Just like taking medicine, you should always know what you’re giving to your pet. So if adverse side effects occur, you can assist the vet in figuring out what went wrong. It’s also best to keep the dewormer container for a few days.

-Observe the pooch

After you or the vet gave your pooch a dewormer, it’s your job to observe the doggo at home. Watch out for any change in behavior, energy level, and appetite. It’s quite reasonable for dogs to eliminate during deworming, but you should also ask the vet what’s normal from alarming.

Also, it will help to jot down your observations together with the time when it happened. This way, the vet can quickly assess the situation if things go south.

Prevention is the key

Just like any disease or infection, prevention is always the key. If your dog doesn’t have any worms, ask the vet for a preventive solution that you can give your pet. This way, your doggo has a defense against the nasty worms that they may get in contact with in the future.

Like what they say, prevention is the best medicine. Being a proactive dog owner goes a long way, especially when it comes to the health of your furry friend.

You can secure a prescription from a veterinarian so your dog will have monthly heartworm medicines. There’s also an anti-heartworm injection that can be administered to your dog every six months.

And aside from being a responsible pet owner, you should also secure yourself. Wash your hands often and don’t let our dogs lick your kids, much so if your Fido just got in from an outdoor adventure.

Final words

How do dewormers work in dogs? In this post, we hoped that we shed light on some questions and concerns that newbie dog owners have about deworming. Always remember that deworming is an important process that should be done with the supervision of a veterinarian. This way, your dog will stay safe and the dewormers will work as expected.