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Heartworm is the rare case where the money argument and the welfare argument point the same way, and where the numbers are large enough that the comparison is not close.
Key figures
- $182.90 Historical study: yearly heartworm prevention spending
- $1,457 Historical study: average heartworm treatment cost
The two numbers
A study of US veterinary practice transaction data, covering August 2022 to July 2023, calculated both sides of the trade:
- Year-round prevention, one year$182.90
- Average treatment of an infected dog$1,457
Treatment of heartworm disease in dogs in the USA, published in Parasites and Vectors. Prevention figure is for owners who purchased year-round; treatment figure excludes indirect costs.
That is roughly an eightfold difference, and the treatment figure does not include the indirect costs: time off work, repeat visits, and the weeks of restriction described below.
Why treatment is harder than it sounds
Killing adult heartworms is not like clearing a gut parasite. The worms live in the pulmonary arteries, and when they die they break up and travel. That is why treatment protocols involve:
- Confirming the diagnosis with antigen testing, and staging the disease with imaging.
- A course of doxycycline, which targets the bacteria that live inside the worms and reduces complications.
- A series of melarsomine injections, deep into the muscles of the back, given over weeks.
- Strict exercise restriction, often for one to two months. This is not optional and it is the part owners find hardest: a young dog on lead-only toilet breaks, for weeks.
Why prevention is prescription-only
A monthly preventive kills larvae acquired in the previous weeks. Giving it to a dog that already carries adult worms can cause a dangerous reaction, so a test comes first. That is also why a lapse matters: a gap of a few months means a new test before restarting, not simply resuming.
Missing doses over the summer and restarting in autumn is not the same as consistent prevention. The study above priced prevention for owners who bought it year-round, which is what the protection depends on.
Making the routine stick
- Same day every month, tied to something you already do on that date.
- Buy a full year when you can, so a missed refill is not a missed dose.
- Annual testing even on prevention, because no product is perfect and a missed dose can pass unnoticed.
- Ask about combined products that cover heartworm plus intestinal worms and fleas, which reduces the number of things to remember.
The adult dog budget places preventive purchases alongside planned visits. The insurance guide keeps policy benefits and exclusions separate from the care plan.
Questions people ask
How much does heartworm prevention cost per year?
The study of US veterinary transactions put year-round purchase at $182.90 a year on average. Individual product prices vary with the dog's weight and with the parasites the product covers.
How much does heartworm treatment cost?
The same study calculated an average of $1,457 for a dog with heartworm disease, not counting indirect costs such as time away from work.
Does my dog need prevention in winter?
Year-round prevention is the standard recommendation across most of the United States, because mosquito activity is unpredictable and monthly products work retroactively on the previous weeks.
What happens if I miss a dose?
Give it as soon as you remember and speak to your vet. If more than a couple of months have lapsed, a test is usually needed before restarting.
Where these figures come from
- Treatment of heartworm (Dirofilaria immitis) disease in dogs in the USA: general findings and cost of disease Parasites and Vectors · pmc.ncbi.nlm.nih.gov
- Heartworm Basics American Heartworm Society · heartwormsociety.org
Figures last checked September 2026.
