Can You Overdose A Dog On Nexgard? (Understanding The Risks)

feeding a corgi a nexgard chewable

If you’ve given your dog the wrong dose of Nexgard, understanding the next steps is crucial

Nexgard is often a safe and effective flea and tick treatment for dogs when used in the correct dosage. If you accidentally overdose your dog, don’t panic. Most dogs tolerate a higher dose without severe side effects. Consult your vet right away if your dog shows any signs of diarrhea, nausea or lack of coordination.

This guide addresses the risks of incorrect dosing, potential Nexgard side effects and how to manage such situations,

What Is Nexgard?

Nexgard is commonly used to eliminate fleas and tick infestations in both dogs and cats. It is a tick and flea treatment that comes in chewable tablets and topical treatments.

It is available as beef-flavored chewable tablets for dogs (NexGard, NexGard PLUS, NexGard SPECTRA).

And topical treatments for cats (NexGard COMBO, NexGard SPECTRA for Cats).

It is also used as an off-label drug for treating demodectic mange, sarcoptic mange, and ear mites in dogs.

NexGard chewable tablets are solely intended for dogs and should not be given to cats.

The active ingredient in Nexgard chewables is Afoxolaner, an insecticide from the isoxazoline chemical group.

Afoxolaner works by attacking the central nervous system of pesky parasites.

Can My Dog Overdose On Nexgard?

Thus, it would take a very high dose of NexGard to cause harm to your dog.

When feeding your dog flea medication, it is always very important to follow the stated dosage.

Mistakes can happen, especially if you have dogs of different sizes.

You might accidentally give your smaller dog the tablet intended for your larger dog.

It is easy to go into panic mode when you realize you fed your dog a double dose of flea medication.

But don’t!

NexGard has a wide margin of safety.

This means there’s a large difference between the usual dose that produces beneficial effects and the dose that can have serious or life-threatening side effects.

Thus, it would take a very high dose of NexGard to cause harm to your dog.

A study was conducted on 8-week-old beagle puppies to evaluate the safety of Afoxolaner, the active ingredient in Nexgard.1

Every dog was given a dosage up to 5 times the recommended dosage.

The dogs were given these high dosages at six intervals over 126 days.

Diarrhea and vomiting were observed occasionally but there were no major side effects.

There are times when your dog might throw up after taking the medication.

In such scenarios, it is best to check with your vet if it is ok to give your dog another dose.

Nexgard Overdose Symptoms

Dogs with a history of neurological conditions should also refrain from taking Nexgard as it can affect a dog’s nervous system.

Although Nexgard is generally considered safe, some dogs may be more sensitive to its active ingredients.

These active ingredients are potent and are needed to get rid of the parasites in your dog’s body.

Giving NexGard to pregnant or lactating dogs is not advisable as the safety of this has not been evaluated yet and doing so could be harmful to the puppies.

NexGard should also be used with caution in dogs that have experienced seizures or neurological issues in the past.

Drugs belonging to the isoxazoline class have been associated with neurologic adverse reactions such as tremors, ataxia, and seizures.

Dogs with a history of neurological conditions should also refrain from taking Nexgard as it can affect a dog’s nervous system.

Even with correct dosing of NexGard, potential adverse reactions include:

  • Nausea
  • Diarrhea
  • Dry skin and dandruff
  • Lethargy
  • Loss of appetite
  • Neurological symptoms
  • Lack of Coordination (ataxia)

These symptoms are only temporary and should go away after a few days.

If the symptoms persist or if you notice any serious adverse effects, please seek medical advice immediately.

I Accidentally Gave My Dog Two Doses Of Nexgard!

woman panicking

First of all, do not panic.

If you gave your dog two doses instead of one, it should be fine given the findings of the above study.

Make sure to keep a close eye on your dog for the next 48 hours.

If your dog shows signs like nausea, diarrhea, or loss of appetite, get vet help right away or call the Poison Pet Helpline.

But if your dog has accidentally ingested the entire box of Nexgard chewable tablets, you need to get your dog to the veterinarian ASAP.

The vet can induce vomiting in your dog to purge out the Nexgard tablets and get treated.

Nexgard Toxicity Treatment

There’s no cure for Afoxolaner poisoning, but certain medicines can help with the symptoms.

The treatment plan will vary depending on the symptoms your dog experiences following a Nexgard overdose.

These can include medicine to ease nausea or anticonvulsants to control seizures.

Supportive care is also crucial for recovery.

This can include fluid therapy, gastric lavage, and decontamination with activated charcoal.

Dietary management is important.

Pet owners may want to offer their dogs a bland diet, such as boiled chicken and plain rice, which can help with tummy distress.

How Does Nexgard Work?

It works by causing over-stimulation of the nervous system of the ticks and fleas.

NexGard enters your dog’s bloodstream within 30 minutes of ingestion.

It works by causing over-stimulation of the nervous system of the ticks and fleas.

This will cause them to be extra active before dying, which is why they may be more visible on your dog’s coat after they ingest afoxolaner from your dog’s blood.

NexGard will kill fleas within the first eight hours of attachment and will work on ticks within 48 hours of attachment.

This makes Nexgard effective as it prevents the adult parasites from laying eggs which can lead to a more serious infestation.

Using a flea comb together with dawn dish soap is also a good way to control flea infestations on your dog.

How Much Nexgard Do I Give My Dog?

NexGard comes in four dosage strengths based on the dog’s weight and is given orally once a month.

Ensure your dog receives the correct dose of Nexgard, based on its weight, to prevent overdose.

Nexgard states that it’s safe for puppies 8 weeks old or older, as long as they weigh at least 4 pounds

Body WeightAfoxolaner Per Chewable (mg)Chewables
4.0 to 10.0 lbs11.3One
10.1 to 24.0 lbs28.3One
24.1 to 60.0 lbs68One
60.1 to 121.0 lbs136One
Over 121.0 lbsN.A.Administer the appropriate combination of chewables

Most dogs should get one Nexgard dose each month, ideally on the same date each month.

This is to be repeated until your dog is clear of the infestation or used during the flea and tick season.

Dangers Of Fleas And Ticks

say no to fleas and ticks signage

These parasites might be small but if left untreated, they can most certainly start to cause serious health problems for your dog.

Ticks transmit several diseases, such as Lyme disease and Rocky mountain spotted fever.

While fleas also transmit and carry pathogens such as tapeworms and the bacteria Bartonella, which can cause bartonellosis in dogs.

These diseases may cause serious harm to your dogs, with clinical signs including:

  • Vomiting
  • Joint inflammation
  • Fever
  • Lethargy
  • Neurological problems

Given that fleas feed on your dog’s blood, puppies and small dogs can eventually become anemic.

In addition, fleas may also cause flea allergy dermatitis in dogs that are allergic to fleas’ saliva.

This will lead to discomfort in dogs, accompanied by itchy, crusty skin, hair loss, darkening and thickening of skin.

How To Keep Fleas And Ticks Off My Dog?

Aside from tick and flea preventatives such as NexGard, here are some other ways that you can try to keep parasites off your dog.

1. Use An Anti-Flea/Tick Shampoo

Using an anti-flea or tick shampoo on your dog every now and then is a good way to help keep the parasites at bay.

This type of shampoo can help control the itch and destroy the parasites at the same time.

Use a fine flea comb and go over your dog’s fur to remove any remaining fleas so that nothing is left remaining on your dog.

To remove ticks, a visual inspection is necessary to manually remove them as they don’t come off by using a comb.

2. Protective Clothing

If you enjoy taking walks in wooded or grassy areas with your dog, it might be a good idea to put protective clothing on your dog’s body and paws.

Fleas and ticks usually live in such areas and can latch or jump onto your dog’s fur. Protective clothing can act as the first line of defense.

Make sure that the clothing is comfortable for your dog and doesn’t cause your dog to overheat.

3. Keep Your House Clean

Do bear in mind that even if you have cleared all the parasites on your dog, they can still live in your home, ready to infect your dog again.

If your dog has had a recent flea or tick infestation, make sure to do a thorough vacuum of your home.

Wash all your dog’s bedding in hot water. If your dog sleeps with you, do the same for your sheets.

Make it a point to do this once a month just to keep your home as parasite-free as possible.

4. Use A Vinegar Spray

Parasites like ticks and fleas aren’t fond of odors that are sharp and acidic like vinegar.

Mix one part apple cider vinegar and two parts water in a spray bottle.

Spray your dog with this mixture and comb it into the fur.

Make sure to not spray the mixture on your dog’s face, especially their eyes, as it can be painful.

You can reapply the mixture on your dog’s fur every few hours or when taking a walk in grassy areas.

I prefer to use vinegar over anything citrusy as some citrus fruits can be toxic to dogs.


Tick and flea prevention is important for your dog’s health and well-being.

If you plan to give your dog anti-parasite medication like Nexgard or anything similar, it is best to have a word with your vet doing it.

Although the majority of these treatments are safe for dogs, there is always a risk of an adverse reaction.


  1. Safety evaluation of orally administered afoxolaner and milbemycin oxime in eight-week-old dogs

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