Does My Dog Need a Heartworm Test?

Does My Dog Need a Heartworm Test?
Photo by Angel Luciano

Did your vet tell you your dog needs a heartworm test?

Did that make sense to you, or did it just seem like another expense at an already expensive vet visit?

Heartworm is serious but usually not well understood by pet parents. This article addresses one of the most common topics I deal with in the veterinary clinic: heartworm testing.

Why Test for Heartworm?

Heartworm tests are essential because early detection can prevent serious health problems. Even if your dog is on preventative medication, annual testing ensures that the prevention is working and that your dog remains heartworm-free.

Heartworm prevention is very very effective, but it is not 100% effective 100% of the time, so that is why testing is important!

How is Heartworm Tested?

Veterinarians use blood tests to detect heartworm proteins in your dog's bloodstream. The most common test is the antigen test (the antigen is the chemical/substance which comes from the heartworm), which identifies adult female heartworms. This test is usually very accurate, but there are other tests your vet may recommend if the result of the first test is questionable.

Puppies under 7 months of age usually do not need to be tested, however, exceptions may occur, so be sure to speak with your veterinarian.

When Should Dogs Be Tested?

  • Annual Testing: Regular testing is recommended even if your dog is on year-round preventative medication.
  • Before Starting Prevention: If your dog hasn’t been on a preventative, they should be tested before beginning the medication.
  • If There's a Lapse in Prevention: If there's been a gap in preventative treatment, testing is crucial to ensure your dog hasn’t become infected.


Heartworm testing is a vital part of your dog's health care routine. Regular tests ensure early detection and effective prevention, safeguarding your pet from this potentially fatal disease.

Call to Action

Is your dog on heartworm prevention? Speak with your veterinarian today about how to protect your dog from heartworm disease.