🫀 Heartworm Prevention Cost Calculator

Prevention Products Compared

All figures above are for a medium dog (25–50 lbs) bought at a standard veterinary clinic, and include the annual heartworm test. Costs above are for the medication itself; some clinics bundle a free or discounted heartworm test with an injectable purchase, so ask before assuming the full test fee applies on top.

Prevention Cost vs. Treatment Cost

This is the comparison that matters most, and it is not close. A year of prevention, including the annual test, runs roughly $75–$360 depending on product and size. Treatment for an established infection runs $400–$2,000 in typical cases, and can climb past $3,000 in advanced or complicated cases needing additional imaging, hospitalization, and extended monitoring. That is commonly 5 to 15 times the cost of a full year of prevention — before counting the physical toll on the dog.

Treatment itself is not simple. The standard protocol involves confirming the diagnosis (antigen test plus a microfilaria test, often chest X-rays and sometimes an echocardiogram to assess damage already done), a course of an antibiotic and sometimes steroids to prepare the dog's body, then a series of melarsomine injections spaced out over roughly two months, with strict activity restriction throughout — because physical exertion while dying worms are breaking down in the bloodstream raises the risk of a fatal blood clot. Recovery is not guaranteed even with treatment, particularly in dogs with a heavy worm burden or existing heart damage.

Safety Notes That Matter More Than the Price

• Test before you start. A dog needs a negative heartworm test before beginning any preventive product. Giving a preventive to a dog that already has an active infection can trigger a severe, potentially fatal reaction as the medication rapidly kills circulating microfilariae in the bloodstream.
• Test annually, even while on prevention. No preventive product is 100% effective, and a missed dose, a vomited chewable you did not notice, or a rare breakthrough infection can happen even with consistent use. The American Heartworm Society recommends annual testing regardless of how reliably you dose.
• Year-round dosing is the actual recommendation, not seasonal. Mosquito activity does not stop cleanly at a calendar line, and gaps in coverage are one of the most common paths to a breakthrough infection. If you select seasonal dosing above, treat the resulting lower price as informational, not as a recommendation.

What About Cats?

This calculator is built around dogs, since dosing, product options, and treatment protocols differ meaningfully by species — but heartworm matters just as much for cats, arguably more. There is no FDA-approved heartworm treatment for cats at all. If a cat becomes infected, veterinary care focuses on managing symptoms and supporting the cat through the infection rather than eliminating the worms, since the treatment used in dogs (melarsomine) is not safe for cats. That makes monthly preventive medication the only real defense for cats in any heartworm-risk area, indoor cats included — mosquitoes get inside, and heartworm disease in cats can look like asthma or simply go undiagnosed until it is serious.

Where to Buy It for Less

Veterinary clinic: the default option and the only place to get an injectable product administered. Convenient, and the exam or bloodwork needed can sometimes be bundled with the visit.

Online pharmacy: oral and topical products can usually be filled through an online pharmacy once your vet approves and authorizes the prescription, and this route is often somewhat cheaper than buying directly at the clinic counter. This option does not apply to injectable products, which must be given in person.

Low-cost or nonprofit clinic: often the cheapest source across every product type, including injectables, though appointment availability and product selection may be more limited than a full-service vet office. Worth checking for seasonal wellness or vaccine clinics in your area.

Frequently Asked Questions

How much is heartworm prevention for dogs?

How much is heartworm prevention for dogs depends mainly on product type and dog size. Monthly oral or topical products run roughly $5-$18 per month, or about $75-$230 per year for a medium dog including the annual heartworm test. Injectable options (given every 6 or 12 months at the vet's office) typically work out to $90-$160 per year depending on dosing schedule and size. Larger dogs cost more across every product type since dosing is weight-based.

Heartworm prevention cost per month

Heartworm prevention cost per month for a monthly oral or topical product is typically $5 to $18, depending on the specific product and your dog's weight (larger dogs need a higher, more expensive dose). Injectable options are not priced monthly since they are given once every 6 or 12 months at the vet, but averaged out they land in a broadly similar range.

Is heartworm prevention worth it?

Yes. A full year of heartworm prevention, even at the higher end of the price range, typically costs a fraction of what treating an active heartworm infection costs, before even factoring in the health risk and physical toll treatment puts on a dog. Heartworm is also almost entirely preventable with consistent dosing, while treatment is not risk-free and does not undo existing damage to the heart and lungs. For cats, there is no FDA-approved heartworm treatment at all, which makes prevention the only real option.

Heartworm test cost

A standard annual heartworm antigen test typically costs $35-$75 at a veterinary clinic. If that test comes back positive, a confirmatory microfilaria test (roughly $20-$40 more) and further diagnostics like chest X-rays are usually the next step before starting treatment. This annual test is recommended even for dogs who are consistently on prevention, since no preventive is 100% effective and a missed or vomited dose can create a window for infection.

Heartworm prevention vs treatment cost

Heartworm prevention vs treatment cost is not a close comparison. A year of prevention, including the annual test, generally runs $75-$360 depending on product type and dog size. Treatment for an established infection generally runs $400-$2,000 or more, and can exceed $3,000 in complicated or advanced cases requiring additional imaging and extended monitoring — roughly 5 to 15 times the cost of a year of prevention, not counting the physical toll of treatment on the dog itself.

Cheapest heartworm prevention

The cheapest heartworm prevention on a per-dose basis is usually a monthly oral or topical product for a small dog, purchased through a low-cost or nonprofit veterinary clinic rather than a full-service vet office. Buying oral or topical products through an online pharmacy with a prescription from your vet is often somewhat cheaper than buying directly at a vet clinic as well. Injectable products must be given at a vet's office regardless of where you shop, since they cannot be self-administered.

Is there a ProHeart 12 pricing calculator?

The injectable option in the comparison above covers ProHeart 12 (moxidectin), the once-yearly heartworm injection for dogs, so this works as a ProHeart 12 pricing calculator. Because it is administered in-clinic and dosed by weight, prices vary more than shelf products and a wellness exam may be required on top. The useful comparison is not the injection price alone but the annual total against twelve months of a monthly preventive — and against the cost of treating an infection, which the calculator also shows.