Heartgard Plus vs. Heartgard for Dogs Which Is Right for Your Canine?

Heartgard Plus vs. Heartgard for Dogs
expert or vet photo
vet verified PetCareRx Staff Veterinarian DVM

Thumbnail of Heartgard Regular for Dogs

Heartgard Regular for Dogs

Heartworm & Deworming
{{petcare_price|currency}} Price in Cart w/PetPlus {{petplus_price|currency}} See PetPlus Price in Cart

Heartgard Plus and Heartgard for Dogs are two of the leading heartworm preventatives on the market. Although their names are similar, they actually have some key differences. Find out more here to help better decide which medication is the best for your dog.

Heartworms can lead to several devastating outcomes, which is why prevention is vital. Heartgard for Dogs helps prevent heartworms, and Heartgard Plus for dogs does triple duty to prevent heartworms and ascarid and hookworm infections.

Heartworms in dogs can cause permanent damage to blood vessels, make breathing difficult, and when left untreated, can cause a pet’s death. So, preventative heartworm medicine for dogs like Heartgard Plus and Heartgard for Dogs are crucial. Treatment for infected dogs can be long-term and expensive, and dog parents must undergo the difficult task of keeping their dogs quiet and calm for many months since excitability and exercise are known to exacerbate a dog’s symptoms and could even lead to death.

Symptoms of Heartworms

Heartworm disease is spread when mosquitoes bite an infected dog and then bite another dog. The worms enter the bloodstream and migrate to the heart and lungs, where they lay eggs. The eggs can remain in the lungs for up to seven years. 

Some of the signs and symptoms of heartworm disease include:

  • Difficulty breathing

  • Dilated cardiomyopathy (DCM) – A condition in which the heart muscle becomes weak and enlarged, making it difficult for blood to pump through the body

  • Enlarged heart – An enlarged heart can lead to shortness of breath, lethargy, exercise intolerance or collapse

Heartworms can also cause symptoms like coughing, difficulty breathing, fainting, loss of appetite and weight loss. A veterinarian can perform an ultrasound or x-ray to determine if your dog has heartworms.

If your dog has heartworms, he'll need treatment right away. He'll receive medication to kill the worms and reduce swelling in his heart that's caused by the infection.

Heartworms are transmitted through mosquito bites, and unfortunately, there’s no way to know if a mosquito was infected, or whether its bite has caused or will cause heartworms. The only way to prevent the onset of heartworms is to arm your dog with regular prevention heartworm meds for dogs like Heartgard. So what are the differences between Heartgard Plus and Heartgard?

What Does Heartgard Protect Against?

Heartgard and Heartgard Plus both protect dogs against heartworm infestation.

  • Heartgard protects against heartworms alone.

  • Heartgard Plus protects against heartworms, hookwormsroundworms, and other ascarids (types of intestinal parasites).

How Long Does a Dose Last?

Each dose of Heartgard or Heartgard Plus lasts 30 days.

Are There Any Side Effects?

Ivermectin is the primary ingredient in Heartgard as well as in Heartgard Plus. Ivermectin in high doses, as is used in cases of sarcoptic mange, for example, can pose some risks. Doses of ivermectin used as heartworm prevention for dogs, however, are relatively low. Therefore, the risks of side effects are also low, with a few exceptions.

Collies and other similar herding breeds are known to have Ivermectin intolerance. For this reason, your veterinarian may wish to use an alternative heartworm prevention treatment. If you have a sheepdog or Australian Shepherd, you may wish to consult your vet before administering these drugs.

What is the Age Minimum for Heartgard?

Neither Heartgard or Heartgard Plus should be given to puppies till they’re at least 6 weeks of age.

Can Heartgard be Administered to Pregnant Pets?

Speak with your vet about giving these heartworm pills for dogs to pregnant dogs. Any medication should be used with great care and caution when it comes to pregnant animals.

How Does it Work?

A dog heartworm med like Heartgard or Heartgard Plus works in essentially the same way. The chemical formulations in each medication are designed to cause paralysis and death in worms, at the larval stage. This means that worms are never able to mature into adulthood or reproduce. They die before they develop, thereby ensuring that your dog will suffer no deleterious effects from their presence.

Other than medication, you can also use the Seresto Flea Collar for dogs to prevent your dog from getting heartworms. This dog collar can also repel mosquitoes which spread heartworms. 



 For the
 Prevention of...

 age of


  Chewable pill form;
  effective 1


  6 weeks or older

  Heartgard Plus 

  Chewable pill
  form; effective 1


  6 weeks or older

What Happens When You Don’t Treat Heartworms in Dogs?

If you don't treat heartworms in dogs, you could end up with a lot of expensive and painful problems.

Heartworm disease is a serious condition that can cause your dog to become very ill and die if left untreated. The worms live in the heart and lungs, which makes it hard for your dog to breathe and pump blood around his body. In addition, the worms can spread throughout your pup's body, including his brain and eyes.

Without treatment, there is no cure for heartworm disease. If your dog has heartworms, you'll need to take them to your vet for treatment as soon as possible so that they don't get worse or die from complications caused by their infection.


More on Heartworms

Top 7 Dog Heartworm Treatments
Signs of Feline Heartworm Disease
Can People Get Heartworms?
Heartworm Tests Explained

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.

Was this article helpful?
Ivermectin Sensitivity Heartworm Hookworm Whipworm Roundworm Tapeworm

You May Also Like

Image for Iverhart Max vs Heartgard for Dogs
Iverhart Max vs Heartgard for Dogs

Heartworm Prevention Medication For Dogs

Read More
Image for Top 7 Dog Heartworm Treatments
Top 7 Dog Heartworm Treatments

The Best Way to Prevent Parasites from Making Your Dog Their Home

Read More