5 things to know when adopting a dog with heartworm

Adopting a dog with heartworm is such a wonderful thing to do. There are so many dogs who need loving homes. When adopting a dog, sometimes it’s hard to know what they have been through or what illnesses they might have. Unfortunately, heartworm disease can be common in rescue dogs. Most dog shelters will test dogs for heartworm disease, especially if found outside as a stray dog. The good news is that heartworm disease is totally treatable and your adopted dog can live a beautiful, long, and wonderful life alongside you. As a new dog owner, it is important to understand a few things about heartworm. Below you will find 5 things to know when you adopt a dog with heartworm.

  1. Understanding what a heartworm-positive dog means
  2. Cost of heartworm treatment 
  3. Long-term side effects of heartworm
  4. Prevention of heartworm 
  5. Benefits of adopting a dog with heartworm
white chow chow dog

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1 – Understanding what a heartworm-positive dog means

Heartworm is when a dog is infested with Dirofilaria immitis. It’s a big worm that I can’t even pronounce but essentially it’s an adult worm that gets into your dog’s heart and causes havoc. The worm is developed from mosquito bites. My assumption is that many shelter dogs end up with heartworm since they are abandoned and left outside, where infected mosquitos bite the dog. 

The challenge with heartworm disease is as more worms grow inside your dog, they go into the blood vessels of a dog’s heart. These worms end up clogging the dog’s heart. This ultimately means that the heart can’t push blood out to the rest of the body and the dog’s heart will begin to fail.  Heartworm affects 1 in 100 dogs every year in the United States and it is a fatal disease if not treated.

Symptoms of heartworm

If you suspect your dog might have heartworm, below are common symptoms to watch out for and speak with your vet about.

  • Cough
  • Lethargy
  • Not wanting to exercise
  • Weight Loss
  • Difficulty breathing
  • Excessive panting

Luckily, most dogs are tested for heartworm at their yearly visit with the vet through a simple blood draw. Also good news, an infected dog is not contagious to another dog. Of course, if you have any concerns about your dog having heartworm, please speak with your vet immediately. 

2 – Cost of heartworm treatment

If you are adopting a dog who already has heartworm, it’s likely that the animal shelter has already begun treatment for them. Let’s take a look at the treatment cycle for heartworm and the cost of treatment at each stage.

Heartworm Testing (~$35-$75)

This is a test that your veterinary team can do and results usually come back immediately. It’s recommended that your dog be tested annually for heartworm so please consider this in your yearly budget for your dog expenses. If a dog is heartworm positive at the time of adoption, the foster family or shelter has likely already had the test completed and you would likely not be responsible for paying for this test.

Confirmatory Test (~$20-$25)

Heartworm treatment is expensive and can have side effects. Therefore, your vet will want to be 100% positive that your dog has a heartworm infection before they begin treating them. This is why your vet will likely do a second blood test to confirm. Again, if you know your dog is heartworm positive from the shelter, then they likely already had this test completed and you would not be responsible for the cost of this confirmatory test. 

Chest X-Ray (~$200-$400) & Ultrasound (~$500-$800)

Once your vet has confirmed that your dog is heartworm positive, they will likely want to perform a chest x-ray and ultrasound of the heart to determine the stage of heartworm disease. This is important so that you and your vet know the severity of the disease and understand what treatment options will be best for your pup. If your dog has already begun treatment at the shelter, these tests would have already been performed as well.

Initial Heartworm Treatment (~$50-$200)

Quick treatment of heartworm is important. Now that you know your dog has heartworm, they will likely begin medications immediately. Dogs will likely begin to take Doxycycline to help weaken the adult worms. Next, they will be given Steroids to help with their cough and help reduce any inflammation they may have.

Next, a prescription heartworm preventive is usually given to a dog on days 1 and 30. This medicine will help kill heartworm larvae.

One of the last steps in heartworm treatment is to kill adult worms. This treatment usually involves a series of injections of melarsomine. This is the most expensive portion of the treatment and can range from $500-$1500. A round of steroids after each injection is also usually recommended.

Follow-up Testing (~$40)

Dogs are tested for microfilaria about 30 days after their 3rd melarsomine injection.

Depending on the results of the follow-up test, additional treatment may be needed that will cost anywhere from $500-$1200. If your dog tests heartworm negative, no additional cost of treatment will be needed. The ongoing cost of yearly tests and heartworm preventatives should still be considered by pet owners so their dogs do not become infected again. Monthly preventative runs anywhere from $20-$50/month and a yearly heartworm test is between $25-$55.

Possible Additional Costs 

Dogs who have advanced heartworm disease may not be able to undergo the typical medication protocol for their treatment. The only treatment that might be available to your dog is to surgically remove the heartworms which can cost upwards of $5,000. Heartworm is a serious disease, but with preventative medications and immediate treatment, the goal is to never get to the point of needing surgery.

little black dog running on the grass

3 – Long-term side effects of heartworm

The most important thing to do when your dog is heartworm positive is to start treatment immediately to reduce the chances of long-term side effects. Heartworm can cause severe lung disease and congestive heart failure. Be sure to check out the American Heartworm Society. This is an amazing resource to find out additional information on heartworm in dogs or other pets.

4 – Prevention of heartworm 

Monthly heartworm prevention is essential to keep your dog’s health in order. All dog owners should speak with their vet about heartworm preventatives for their dogs. Most prevention meds are a monthly oral or topical treatment. You can find a variety of heartworm prevention medications that will fit your budget, dog’s weight, and needs. For dogs that are not a fan of fake treats, a topical treatment might be better for them.

5 – Benefits of adopting a dog with heartworm

Let’s talk about some of the amazing benefits of adopting a dog with heartworm. 

  • Netflix and Chill Buddy: Dogs who are receiving heartworm treatment are required to limit their exercise.
  • They make for great apartment dogs: During treatment, dogs will have to limit their walks and active outdoor time. 
  • You get to save a dog! Adopting a dog from a shelter is amazing! It helps provide a home to a dog that otherwise might not get one. Most shelters will cover the initial cost of heartworm treatment for your dog even after you adopt them.
two golden retrievers playing

A quick story about adopting a dog with heartworm

My sister has actually adopted three dogs from different shelters. Two dogs were heartworm-positive when she adopted them and the different shelters covered the cost of their treatment. I am happy to say that both of these dogs have been thriving and living their best life since undergoing treatment a few years ago. And you honestly, would not even know that they ever had heartworm before or went through treatment. All this to say, adopting a dog with heartworm is a great thing to do and helps provide a loving home and continued heartworm prevention for the pup.


Heartworm is something that all dog owners, whether they adopt or have a new puppy from a breeder, should be aware of. All dogs should be tested yearly and should also be on monthly preventative. That said, many rescue dogs may have heartworm because they were not on a preventative heartworm medicine if they were stray dogs. It’s important to understand the treatment and cost associated with adopting a heartworm-positive dog, but know that most animal shelters will cover the medical cost of initial treatment. 

The great thing about adopting a dog who is heartworm positive is that for many months, they are on strict exercise restrictions. This makes for a great cuddle buddy on the couch! To find other ways to keep your dog healthy, check out some of the supplements on this site. If your new dog is a puppy, be sure to read about all the things to get for them.

Comment below if you adopted a dog with heartworm and what your experience was like.