Ask Seth: Heartworms for Indoor Dogs

We've never had a problem with heartworms, and our dog is mostly indoors. Can we skip it this year?


Dear Seth,

My vet prescribes heartworm preventative for my dog Sherri every year. We have never had a problem with heartworms and are considering not getting the medication this year. She spends most of her time indoors and I think she would be fine without it. Is heartworm preventative necessary for Sherri? If she gets heartworm, is it that serious?

Want to learn how to save on heartworm treatments? Click here
Want to check pricing and try our veterinary discount program, risk-free? Click here

Every dog that lives in an area with mosquitoes is at risk for heartworm. When a mosquito bites an infected dog, it ingests the heartworm larvae. If that same mosquito bites your dog, your dog will become infected as well.

Preventative medicine is nearly 100% effective when given as directed.

There are several factors that determine how heartworm will impact your dog:

  • severity of infestation (number of worms)
  • your dog’s immune system
  • your dog’s activity level
  • length of time of infestation

Active dogs tend to get more severe cases of heartworm. Larger dog usually tolerate heartworm better that smaller breeds.

Symptoms of heartworm disease include:

  • coughing
  • muscle weakness
  • weight loss
  • shortness of breath
  • vision problems

Your vet can perform a simple blood test to diagnose heartworm disease. Heartworms can grow from microscopic to up to 16 inches in size. Larger worms can be detected on x-rays.

The earlier heartworm is detected, the more successful treatment will be. Treatment varies according to the severity of the infestation. Severe cases may require complicated and expensive treatments. There are medications that are effective in eliminating the heartworm. Your vet will determine the best treatment approach for your animal based on the severity of the infestation and your animal’s personal medical background and characteristics.

It is clear that preventative medicine is the best way to protect your animal from heartworm!


Seth Mayersohn, CVT

Welcome Veterinarians

Pet Assure is the largest veterinary network in the U.S. with over 5,600 veterinarians.

Pet Assure powers DVM Network, a brand built to support our participating veterinary professionals and help them grow their practice.

Visit to learn more.