Can Heartgard Be Cut In Half? 3 Reasons Not To

Zack Keithy, our author, is a certified veterinarian technician (UC Blue Ash) for over 6 years (contact him here). The articles written here are based on his expertise and experience, combined with a review by our expert vet reviewers including Dr M. Tarantino. Learn more about us here.

Heartgard is a popular medicine for dogs that protects against heartworm disease, which can be very serious for your pet.

It comes in the form of chewable tablets and does not require refrigeration or special handling.

However, many people want to know if they can make the Heartgard pills smaller so that they last longer and are easier to give to their dogs.

So, can Heartgard be cut in half?

The answer is no, Heartgard should not be cut in half. The medicine is designed to be taken as a whole tablet and may not work as prescribed if you try to break it up into pieces or cut it into halves.

There are some important things you should know before you start cutting up your dog’s medication—we’ll cover those here.

Doggy says, read this too: Heartworm in Dogs: Treatment and Post Care

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Why You Should Not Split Heartgard Medicine in Half

We get it. Taking care of a dog does cost quite a fair amount of money, especially when it requires medicine regularly.

Lots of pet owners we speak to have similar concerns, thus resorting to some actions such as:

  • Cutting down the budget
  • Reducing costs by trying to find alternatives
  • Splitting up medicine in order to give two or more dogs in their household

However, in order to ensure the health of your dog is in the best order, it is important to give them the exact dosage that the vet prescribed.

Skimping on them might lead to very undesirable effects and harm your dog!

With that out of the way, read on for some of the key reasons you should not cut Heartgard Plus in halves.

Why You Should Not Split Heartgard Medicine in Half

1. Not having the right amount of medication

The majority of heartworm preventive medications come in the shape of delicious soft chews or flavored tablets.

Additionally, they are combined with medication like ivermectin meant to ward off heartworms or other parasites.

If you divide the medication in half, one half might have all of the medication while the other might not.

The required medications are fully dosed in the pill, but they are not dispersed uniformly across the entire pill.

That is the main reason why you should never attempt to split Heartgard into halves or any medication for that matter.

2. Lose efficacy

Another important thing you should know is that when you split a Heartgard tablet or soft chew in half, it will start to lose its efficacy quickly.

By the time you reach the next month when you want to feed your dog again, the medication is very likely ineffective already.

3. Not recommended by the manufacturer

And lastly, the manufacturer of Heartgard Plus has stated clearly in its factsheet that the dosage must be administered whole and does not indicate anywhere that it is safe to split in half.

Assuming that you feed your dog halves only and end up not being able to prevent heartworm in it, I am sure the manufacturer can excuse itself from being responsible.

There is also lots of advice from vets online to not split the medicine in half.

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Can I Give My Dog a Lower Dose of Heartgard?

Some pet owners might be concerned with overdosing, especially when they have very small dogs.

That’s a legitimate concern.

If my dog weighs only 3 pounds or less, and you are asking me to use a medicine suitable for a dog up to 25 pounds, I would naturally be quite worried.

However, we have checked with a few vets and luckily, there is almost zero chance of your small dog overdosing on the medicine.

Problems only tend to arise due to allergies, rather than the medicine being too much.

You may wish to verify this is your vet too if you are still worried.

Alternatively, you can also consider other types of heartworm medicine such as Interceptor Plus.

Doggy says, this might interest you too: Are Eggs Good for Nursing Dogs? [How to Feed?]

Can I Give My Dog a Higher Dose of Heartgard?

There is no need for you to give your dog a higher dose of Heartgard.

However, if you accidentally gave your dog an extra dose once or twice, it will be fine and won’t have any significant unpleasant symptoms at all.

This is because both of its active components, ivermectin and pyrantel pamoate, have exceptionally broad margins of safety.

Doggy says, you might be keen to read this too: Gave my dog heartworm pill early

How Much Does Heartgard Cost?

Heartgard Plus is a prescription medication and therefore it’s very important that you speak with your veterinarian before making any decisions about how to use this product.

The price of Heartgard can vary depending on where you purchase it from as well as the packaging size, so let’s take a look at some of the different places where you can get your hands on this medication:

  • Petco: $45.99 ($43.00 for repeat orders) for six chewable tablets (1-25 lbs dog)
  • 1800-PETMEDS: $45.99 for six chewable tablets (1-25 lbs dog)
  • PetSmart: $45.99 for six chewable tablets (1-25 lbs dog)
  • Walmart PetRx: $45.99 for six chewable tablets (1-25 lbs dog)

Doggy says, you might be interested to read this too: Liquid heartworm medicine for dogs

Heartgard Plus dosage recommendation for dogs

Here is the information extracted from the factsheet.

Dog WeightChewables per monthIvermectin ContentPyrantel ContentColor Coding
Up to 25 lb168 mcg57 mgBlue
26 to 50 lb1136 mcg114 mgGreen
51 to 100 lb1272 mcg227 mgBrown

Frequently Asked Questions (FAQs)

What does Heartgard treat?

Heartgard treats heartworm disease, a serious infection that can be fatal to your dog. This disease is spread to dogs through the bites of infected mosquitoes. Heartgard helps prevent heartworm disease by killing the worms before they grow into adults and multiply in the bloodstream. It comes in the form of a chewable tablet that’s given once every month to dogs six weeks of age and older and is safe for dogs of all sizes regardless of weight, including pregnant or nursing females.

How to give your dog Heartgard tablets?

Give Heartgard to your dog once a month, either on its own or you can break it up and mix them in with your dog’s food. Be sure to follow the directions on the label carefully and not skip any dose.

In Conclusion: Can Heartgard Be Cut In Half?

There are many reasons why someone may want to cut Heartgard tablets in half.

No matter what the reason is though, it would be highly advisable not to do that to ensure your dog gets the full medication it needs to prevent heartworms.

Caring for your dog is not easy, which is why we have lots of useful articles such as whether belly bands can cause UTI in dogs, feeding your dog more than 1mg of Ativan, using Steri strips for your dog, and many more.

You’ve made it to the end, but I hope it’s not the end of our journey. We want to hear your voice! Share your thoughts, problems, suggestions, or anything related to your dog in the comments section. And don’t forget to join our newsletter today too.

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Zack Keithy
Zack Keithy

Hey, I'm Zack, the Chief Editor here. I was formerly a Certified Veterinary Technician (CVT) for a good 6 years before moving on to greener pastures. Right now, I am still heavily involved in dog parenting duties, and it is my desire to share all our knowledge with fellow dog owners out there! Connect with me on LinkedIn, or read more about Canine Care Central!


  1. Absolutely, I was always wondered about this. Thanks for shedding light on why it’s best not to cut Heartgard – our pets’ health is too precious to take chances!

    • Hey Paul, yes you’re absolutely right. We have to be super careful since they can’t take care of themselves! And I also wanted to emphasize that when it comes to medication like Heartgard, we should always stick to the dosage, and not give our dogs a lower or higher dose without any expert advice!

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