How Long Do Dewormers Take to Work: Most Common Types

Our four-legged friends are often of the curious variety, and that curiosity can land them in some pretty sticky situations—like getting worms. These intestinal parasites are not only icky, but they can also be dangerous to your pup’s health if left untreated.

Fortunately, deworming dogs is a relatively simple process that gets rid of these unwelcome guests for good. But how long do dewormers take to work exactly? The answer is, of course, it depends.

How Long Do Dewormers Take to Work

The length of time it takes for a dewormer to work depends on the type of worm your dog has and the severity of the worm infestation. Those with a more severe case of worms may need to be treated with a higher dose of medication or for a longer period of time than those with a milder infestation.

In general, most dewormers will start working within two to six hours after administration. However, it may take a few days to see the full effects of the medication as the worms are gradually eliminated from your pup’s system.

How Do Dewormers Work

Sure, the timeframe of operation for deworming medicine for dogs is a vital piece of the puzzle, but it’s their method that’s really interesting. These medications work by either paralyzing and breaking up the worms so they can be passed through your dog’s system or by preventing the worms from being able to absorb nutrients, which ultimately leads to their extermination.

Now, you may see a whole worm in the puppy poop after deworming or a segmented speciment that looks like a grain of rice—this is completely normal! This means that these parasites and their worm eggs are no longer hanging out in your pup’s intestines and causing problems.

What to Expect After Deworming a Dog

If you’re using a deworming tablet to get rid of the parasite eggs, you need to make sure your canine companion has swallowed the entire pill. If not, the dewormer won’t be as effective. In some cases, pups may throw up after taking the medication—if this happens, you can try hiding the pill in a bit of cheese or peanut butter to make it more palatable.

After giving your pup their deworming medication, there may be some signs of general discomfort like bloody diarrhea, vomiting, intestinal blockage or a decrease in appetite. These side effects are usually mild and should dissipate within a day or two. However, if they persist or seem to be getting worse, you need to contact your veterinarian right away.

They may start scooting their butt along the ground to relieve irritation caused by the worms in their intestines. You can try some home remedies for dog scooting to make them more comfortable until the dewormer takes effect.

If you keep asking yourself ‘How long after deworming will my dog pass worms?’, you’ll likely have to wait a few hours to see any results. It partially depends on the partiuclar medication you’re using as well as your little friend’s specific condition. In any case, your pooch should be parasite-free once the treatment is fully completed.

How Long Do Dewormers Last

As a general rule, you should deworm your pooch about once every three months. Of course, there are always exceptions to the rule. If your dog spends a lot of time outside, for example, they might be more susceptible to parasites and you might need to deworm them more frequently.

The same goes for puppies, who are more likely to pick up worms since they’re still building up their immune system. The parasites may also be more difficult to get rid of if your dog has a weakened immune system for any other reason.

Most Common Types of Dog Worms

These little critters can do a whole lot of damage, and they’re classified according to how they infect their hosts. The basic types of worms are roundworms, hookworms, tapeworms, whipworms, and heartworms.


Also known as Toxocara, these parasitic worms have an elongated, cylindrical shape that can grow up to seven inches in length and tend to be light gray or white in color. While they’re not usually fatal, they can cause a host of problems like diarrhea, weight loss, vomiting, dehydration and a pot-bellied appearance.

In terms of life cycle, roundworms typically spend part of their time in an animal’s intestine and the other part in the environment in the form of eggs. These eggs can then be ingested by other animals—including humans—and the cycle starts all over again.


As their name implies, hookworms have sharp, hooked mouths that they use to attach themselves to the intestinal walls of their hosts. These blood-sucking parasites can cause and weight loss in severe cases, and they’re especially dangerous to young puppies that can easily become dehydrated.

Since these parasites absorb blood from their hosts, they can cause anemia—which is a condition characterized by a low red blood cell count. It can make your pet seem lethargic and weak and can even be fatal if left untreated.

Evidently, their feeding habits take a toll on a dog’s health, and they can also be passed from mother to puppies during pregnancy or through the milk while nursing. They have a fairly long life span and can survive in the environment for several years.


These flat, segmented worms can grow up to an impressive 28 inches in length and live in the intestines of their hosts where they feed off of partially digested food. They don’t typically cause serious health problems, but they can be a nuisance nonetheless.

The main way tapeworms spread is through fleas—if your dog swallows an infected flea while grooming, they can end up with these long-term visitors. Another way they can be transmitted is through contaminated food or water, something that’s more likely to happen if you have an outdoor pet.

The best way to treat these is usually through ingestible flea meds and treatments.


These parasites get their name from their long, whip-like tails, and they’re one of the most difficult types of worms to eliminate once they’ve taken up residence in your dog’s intestines. Their stubborn nature is due to the fact that they live in the cecum—the blind pouch at the junction of the small and large intestine—which makes them harder to reach with medication.

Their superior hiding spot also makes these larvae harder to detect, and many pet owners don’t realize their furry friend has whipworms until the condition has progressed and caused some serious damage, including lethargy, bloating and bloody stool.


Perhaps the most lethal of all, heartworms are spread by infected mosquitoes and can quickly lead to heart failure in dogs. These long, thin parasites travel through the bloodstream and eventually end up in the heart and lungs where they result in serious health problems—and even death.

There have been a few cases where a puppy died after deworming was performed for this particular strain of parasite, mainly due to the heavy load of parasites present and the sudden release of toxins when they died. Sometimes there might even be an allergic reaction to the medication itself, though this can be managed with a simple antihistamine.

Either way, prevention is always the best medicine when it comes to heartworms, and pet owners should consider giving their dog regular heartworm medication—especially if they live in an area where these mosquitoes are prevalent.

Frequently Asked Questions

Do worms come out after deworming in humans?

Yes, you may see worms in the stool after taking a dewormer. This is normal and means that the medication is working. Some might still be flicking around, while others might be completely paralyzed.

How do I know if the deworming worked?

Dewormers usually have a few tell-tale signs that they’re working, including vomiting, diarrhea, general weakness, and weight loss. This is how the body expels the parasites, so don’t be alarmed if any of these reactions occur.

Key Takeaways

Taking care of our furry friends is always a top priority, and that includes keeping them free of parasites. Though there are many different types that can infect dogs, the good news is that they’re all treatable—and most are even preventable.

And how long do dewormers take to work? Well, that depends number of factors, including the type of parasite and the severity of the infestation. But as a general rule, you should start to see results within in a couple of hours.

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