Heartworm Symptoms In Dogs: Here’s What to Look for

Heartworm Symptoms In Dogs: Here’s What to Look for

What are the symptoms of heartworms in dogs? We answer this question and give tips on how to avoid heartworm symptoms and keep your dog healthy.

Every pet parent’s nightmare is something terrible happening to their dog. They really are family to us, and for some people, they are like our children or the best friends we have. So today’s topic is a hard one; we aren’t here to alarm you or upset you, but there are some really important things you need to know about heartworm symptoms and what that could mean for your dog.

The American Heartworm Society reports that “More than 20 species of mosquitoes harboring the infective stage of heartworm larvae have been collected in field studies.” This means that your dog needs to be protected from those infected mosquitoes no matter what area you live in the world. In the US, heartworms are most prevalent along the Atlantic coast, the Gulf Coast, and the Mississippi River and its tributaries. Heartworms have been reported in all 50 states.

Let’s cover what you need to know in the least “horrifying language” we can...and remember, this is all to be informative and to encourage you and all pet parents to prioritize your dog’s health and well-being. Sometimes that’s pretty easy, like keeping up with their healthy diet, regular exercise, CBD oil for dogs, cuddles, and all the other things you do to make your dog feel safe and happy.

But for some things, like heartworms, you have to have veterinary care in place for your pet. There’s no other alternative if you want to prevent or treat something as serious as heartworms.

Key Questions We’ll Answer Today


  • What are heartworms?
  • What are the symptoms of heartworms in dogs?
  • What happens if your dog gets a heartworm?
  • What are the best ways to prevent heartworms in your dog?


microscopic view of a heartworm


What Are Heartworms?

Heartworms are actual worms, very long ones, and they live inside your pet, making your pet very sick. They prey on the host’s heart and lungs – and that host could be your precious dog. If that’s not panic-worthy, I don’t know what is. If you aren’t aware, heartworms are a very serious condition in your dog. It could potentially be fatal. So, let’s take a look at how your dog gets them.

Without a full biological analysis of a parasitic relationship (yuk!), let’s just address the parts you need to know so you can take care of your doggie and avoid those terrible heartworm symptoms.

How Does a Dog Get Heartworms?

The parasitic worms, Dirofilaria immitis, get into your dog when infected mosquitoes bite them, and unfortunately for your dog, they become a part of the parasite’s life cycle. Your dog will become a host for worms that mature into adults and produce offspring while living inside your pet.

Other mammals can also contract heartworms – cats, ferrets, foxes, wolves, coyotes, sea lions, and on rare occasions, humans. Remember, only an infected mosquito can spread heartworms, so if your dog has heartworms, they are not a threat to you or your other pets.

Factors that Contribute to the Spread of Heartworms

Mosquito feeding habits can spread heartworms more efficiently when other factors are in place:


  • Travel of infected pets and animals
  • Neglected outdoor infected pets and animals
  • Presence of wildlife carriers in your area
  • Presence of other infected mosquito populations in your area
  • Numbers of animals not on heartworm preventative measures


Interactions between infected mosquitoes and their feeding sources contribute to the life cycle of heartworms, potentially posing a threat to other animals. You really want to be sure your dog isn’t a part of this life cycle, as it can make your dog very ill. Untreated cases of heartworms can even lead to the death of the host animal, including dogs and cats.

What Are the Symptoms of Heartworms in Dogs?

The heartworm symptoms you need to look for are a guideline – not a diagnosis. Only your vet can run the tests necessary to diagnose heartworms in your dog and then prescribe treatment for their care.

Heartworm Symptoms


  • Mild, persistent cough
  • Reluctance to exercise
  • Fatigue after moderate activity
  • Decreased appetite
  • Weight loss
  • Heart failure or cardiovascular collapse in advanced conditions
  • Appearance of a swollen belly due to excess fluid in the abdomen
  • Heartworm blockages can lead to difficulty breathing, pale gums, and dark bloody or coffee-colored urine


The more progressed your dog’s condition, the more you will see symptoms, so it’s crucial to have your dog checked regularly – ideally every year – for heartworms and other parasitic conditions that might make your dog ill.

 ill basset hound laying on sofa

What Should You Do About Heartworm Symptoms?

The first thing you should do if you note any symptoms of heartworms in your dog is to get them to their veterinarian quickly. Their vet will run the appropriate diagnostic blood tests and confirm if your dog does or does not have heartworms.

How Are Heartworms Diagnosed?

Your dog’s vet will run heartworm testing on your pet; you should have this done every year. Your dog must have a negative test before they start most heartworm preventatives. You’ll likely have to take your dog in for the screening visit first, and that cost varies by economic area and individual veterinarian. You may have to go in for a second visit to discuss your dog’s testing results and preventative measures that you can take to protect them.

Because this condition is progressive, meaning the longer your dog has it, the more they can suffer, you’ll want to get ahead of the game, so to speak. Prevent early and diagnose early for your dog’s best chance at beating this condition and living a long, healthy, heartworm-free life.

Can Heartworms in Dogs Be Eliminated?

Yes, they can, but without your dog taking a preventative, they can contract heartworms again. Here’s how heartworms are eliminated from your dog:


What Do I Do if My Dog Has Heartworms?


  • Confirm the diagnosis
  • Restrict exercise for your pet
  • Begin veterinary care immediately
  • Follow up with retesting and preventatives


Heartworm Prevention Tips


  • Pre-screen for heartworms at the veterinarian’s office and put your dog on preventatives
  • Remove sources of standing, stagnant water on your property to eliminate some potential breeding sources for mosquitoes.
  • Try these helpful tips for keeping mosquitoes off your dogs.



person giving cbd dog chew to small dog


This Article Is Brought to You By cbdMD

We try here at cbdMD to address topics of concern to all pet-loving folks who use our products and work very hard each day to prioritize their pets’ health and wellness. It’s not easy sometimes. So, we plan our blog work here to serve your greatest questions about your pets and the things that keep you up at night. We also write a lot of fun stuff that reminds you that you are a part of a larger community of people who want their pets to have the best life possible.

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We hope this article answers your question – what are the symptoms of heartworms in dogs? To be clear, we wanted to remind you to prevent those heartworm symptoms by keeping your dog free from the infestation in the first place. Your dog’s health and wellness, their quality and length of life, all depend on the actions you take to prevent heartworms.

If you have not discussed your dog’s heartworm prevention with their vet or you have been procrastinating on this – we encourage you to make your dog’s appointment today!