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Heartworm Testing FAQ

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Does my dog need a heartworm test before starting preventive medication this season?

Ideally we recommend all patients have a negative heartworm test (a blood test) prior to starting heartworm preventive medication each spring. There are, of course, other factors to take into account such as cost, patient stress and your risk tolerance when making the decision whether or not to test every year.

Why are heartworm tests recommended?

Making sure your dog is negative for heartworm prior to starting preventive medication is the best way to reduce the risk of adverse effects from preventive medications.


Also, while heartworm disease is uncommon in Ontario, it can be very serious when it happens. The best way to prevent irreversible damage is through early detection and treatment, in addition to regular prevention.


What are the risks involved with not doing a heartworm test every year?

If a dog who is positive for a heartworm infection is given preventive medication it can result in serious side-effects resulting in shock, or even death. That being said, this was more of a concern with the older generation of heartworm drugs, and newer drugs are much safer. For example, the drug we most commonly recommend is called Nexgard Spectra. This drug has safety studies demonstrating no significant adverse effects even when given at 5 x the regular dose to dogs with advanced heartworm infections. Every heartworm preventive medication sold in Canada states on the label that heartworm testing is recommended prior to use. In the event you elect to forego testing your veterinarian can still prescribe this medication "off-label". Also, it is worth noting, the Canadian Parasite Expert Panel (CPEP) is now suggesting it may be safe to extend the testing interval (for example, to every 2 years) based on a risk assessment made by you and your veterinarian.

How can I schedule a heartworm test for my dog?

Please email us at, or call us at (613) 230-2106 and we'd be happy to book a visit with you soon! This testing can be rolled into one of your regular in-home veterinary visits, or if you'd just like the test, it can be booked as a visit with our team of registered veterinary technicians. The cost for a technician visit and the test is $118 including tax for members, or $231 for non-members.

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