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What Happens If You Give A Dog Too Much Wormer? [Typically]

It’s imperative to keep your dog up to date with their deworming treatment. There can be severe health implications if your dog becomes infected with worms. You may have wondered exactly how often you should be deworming your dog, or you may have accidentally given your canine friend a higher dose of wormer than they need. It’s only natural to be worried about the potential side effects. So here is what you need to know.

What happens if you give a dog too much dewormer? If you give a dog too much wormer, they might experience unwanted side effects ranging from mild to more severe symptoms. Too much wormer can cause vomiting, diarrhea, and other health problems. Consult your vet immediately if you think your dog has had more than its recommended dose. 

While most worming treatments are extensively tested and have a high margin of safety, overdosing can cause problems, and there are some essential things to be aware of as a dog owner.  

Whether you are using a deworming tablet or a spot-on treatment, this article will answer some of the most common questions owners have when removing these hitchhiking parasites.

Can You Worm Your Dog Too Often?

It’s possible to deworm your dog too often. In fact, treating your dog for worms too much can make your dog unwell. 

When it comes to treating your dog for worms, more frequent treatment is not always better. 

Deworming treatments, also known as anthelmintics, are designed to keep your dog worm-free for weeks to months at a time. 

Most worming treatments work by releasing chemicals that starve or paralyze any worms that may be present within your dog’s gastrointestinal system. 

Once killed or paralyzed, the worms can then safely be excreted by your dog in their feces. 

While many worming treatments will get to work within a few hours, some may take longer to take effect. 

You might not even see any worms passed in your dog’s feces, but this doesn’t necessarily mean that the treatment hasn’t worked. 

If this is the case, don’t treat your dog again too soon, as this can result in an overdose. 

If you think your dog still has worms despite giving deworming treatment then seek advice from your vet.

If your dog is a scavenger and likes to eat anything and everything while out on walks, they don’t always need deworming too regularly; treatment every 1-3 months will usually suffice. 

Anthelmintics work by purging any worms present in your dog’s gastrointestinal system at any one time. 

After the worms have been killed and excreted out, worms can gradually accumulate as your dog eats things they shouldn’t do that may be infected with worm eggs. 

Over time the worm burden can build up until the point where your dog needs deworming again. 

However, giving worming treatment more often than necessary can cause your dog to become unwell, so owners shouldn’t get too carried away with treatment. 

Can Deworming Kill A Dog?

It’s extremely unlikely that worming treatment would kill a dog. Most worming treatments are tested at a range of different concentrations, and there is a wide dosing margin before you would start to see severe side effects of overdosing.

In fact, it is more likely that your dog might die due to an active infection of worms than due to the worming treatment itself. 

The one exception to this is in cases of a severe allergic reaction.

It is always possible for a dog to have an allergic reaction to any treatment, although in the case of worming treatment this is a rare occurrence. 

Mild side effects such as loose stools can occur in some dogs, but this will usually clear up quickly. 

However, some dogs may exhibit more severe side effects such as vomiting, diarrhea, and even swellings or hives over their body. 

If your dog has an actual anaphylactic reaction to the worming medication, they may not be able to breathe correctly as the airways swell up, reducing the airflow in and out of the lungs. 

This is an extremely uncommon occurrence but not impossible, so it’s essential to be aware of it.

If you think your dog has had any of the reactions mentioned above when given a particular worming medication, then take them to your local veterinarian immediately.

How Many Times Can You Deworm A Dog?

Adult dogs should be dewormed at least every 3 months depending on how much of a scavenger they are. If your dog likes to drink out of dirty puddles or eat anything that they come across while out on a walk, then they are at higher risk of parasitic infection and should be wormed more frequently. If this sounds like your dog then worming them every 1-2 months might be necessary. 

Don’t deworm your dog any more frequently than monthly without consulting your vet. 

As mentioned before, if you’ve recently given your dog a worming treatment and are worried that it didn’t work or if you think your dog may have spat the tablet out, then never repeat the worming treatment straight away, unless you are absolutely certain that they didn’t take it. 

It can take a few days to see the effects of the worming treatment, so giving them too much deworming medication too quickly can lead to undesirable side effects. 

If you are unsure how often you should be deworming your dog, then consult your veterinarian, who should be able to recommend a suitable anti-parasite routine.

When Should You Deworm A Dog?

There is no particular time of year when your dog will need worming. Some dogs may be more prone to parasitic infection during the winter and others during the summer – many owners will give deworming treatment less frequently when their dog is at a lower risk. 

As a general rule, most adult dogs will need deworming every 3 months and puppies will need treating more frequently.

Puppies are much more susceptible to worm infections than adult dogs and therefore need deworming treatment more regularly. 

Adult dogs have a fully developed immune system that can help keep a worm burden at bay; adults are also generally less likely to eat anything that they come across. 

Most puppies, however, will become infected with roundworms either before birth in utero or shortly after birth via transmission through their mother’s milk. 

Even if your puppy seems healthy, they are likely to have some worms living inside their intestinal tract and can go on to transmit worms to other dogs or even people through shedding of worm eggs in their feces. 

On top of this, puppies like to explore the world through their mouth and so are at a higher risk of picking up worms this way.

  • Puppies should first be dewormed at 2 weeks of age and subsequently dewormed every 2 weeks after this. 
  • Once they are 12 weeks old they can then be dewormed every month until they are 6 months old. 
  • After 6 months of age most dogs will stay worm-free when they are dewormed every 3 months. 

What To Expect After Deworming A Dog?

Shortly after giving your dog their worming treatment, whether it be a tablet or spot-on, monitor for any signs of adverse reaction. In most cases you won’t notice an obvious change in your dog but in the rare situation that they have an allergic reaction, speak to your vet immediately.

Most deworming treatments work quickly and will start to kill intestinal worms from 2-6 hours post-administration. 

Depending on what active ingredient is in your deworming treatment, you may start to see worms in your dog’s feces.

Some dog wormers work by preventing worms from absorbing sugars that they need for energy; this leads to paralysis and eventual death of the parasites. 

These worms are then often excreted in your dog’s feces, so if you see parts of worms in your dogs’ poop, don’t panic – in fact this means that the treatment has been successful! 

Other wormers kill and break down the worms into smaller pieces, so you may not always see traces of worms in your dog’s feces, but this doesn’t necessarily mean that the treatment hasn’t worked.


Giving your dog more than the recommended dose of any medication can be dangerous. 

While most dogs will only experience mild side effects of an overdose of wormer, some may become more seriously ill, and others may even have an allergic reaction. 

If you think that this is the case then avoid that particular worming treatment in the future and instead try a different active ingredient or brand. 

Never give your dog more than their recommended dose of anthelmintic, and get professional veterinary advice if you think your dog is showing side effects of overdosing.

Related Questions

Can I Worm My Dog Twice In One Week?

It comes strongly advised not to worm a dog twice in one week unless you are certain that your dog spat out or did not swallow the first serving. Different dewormers will have different potencies, but either way, overdosing on this treatment can be dangerous. Instead, it is best to consult with your vet should you feel the need to worm more frequently than once every 3 months.

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