Treating heartworm in a dog typically costs between $1,000 and $3,000 in total, though severe cases requiring surgery can push the bill to $6,000 or more. The wide range depends on your dog’s size, the severity of the infection, and where you live. Here’s a breakdown of what you’re actually paying for at each stage.
What the Full Treatment Involves
Heartworm treatment isn’t a single vet visit. It’s a multi-month process with several phases: diagnostic testing, weeks of preparatory medications, a series of three injections to kill the adult worms, and months of strict rest afterward. The American Heartworm Society recommends this phased approach for all infected dogs, whether they’re showing symptoms or not. From diagnosis to the final injection, the treatment timeline spans roughly 90 days, and full recovery extends well beyond that.
Diagnostic and Staging Costs
Before treatment begins, your vet needs to confirm the infection and assess how much damage the worms have caused. The initial heartworm antigen test averages about $57. If that comes back positive, expect additional bloodwork to check your dog’s organ function and overall health. A basic blood panel (CBC and chemistry) runs around $188, though individual tests like a CBC alone average $78. Chest X-rays are also standard to evaluate the heart and lungs, which adds another cost on top of bloodwork. All told, the diagnostic phase alone can run a few hundred dollars before any treatment starts.
Pre-Treatment Medications
Once your dog is confirmed positive, the next step is a four-to-six-week course of an antibiotic (doxycycline) paired with a steroid. The antibiotic targets bacteria that live inside the heartworms, weakening the parasites and reducing the risk of a severe inflammatory reaction when they die. The steroid helps manage inflammation throughout treatment. This phase costs $30 to $150 depending on your dog’s size and how long the course lasts. Your dog will also be started on a monthly heartworm preventive to kill any immature worms circulating in the bloodstream.
The Injection Series
The core of treatment is a series of three injections given deep into the back muscles. The first injection happens around day 60 of the protocol. A month later, the second and third injections are given 24 hours apart. These injections kill the adult worms living in the heart and pulmonary arteries.
This is the most expensive part of the process. The injections plus associated hospital care typically cost $500 to $1,500, with your dog’s weight being the biggest variable. Larger dogs need higher doses, and the medication itself is costly to manufacture. A 15-pound dog will be on the lower end of that range; a 90-pound dog will be closer to the top.
Exercise Restriction and Follow-Up
One cost that doesn’t show up on your vet bill is the lifestyle change required during treatment. Exercise restriction starts the day your dog is diagnosed and continues for months. The most critical period is the four weeks after each injection, when dead and dying worms are breaking apart and being absorbed by the body. Physical activity increases blood flow and raises the risk of worm fragments blocking blood vessels in the lungs, a potentially fatal complication.
Strict rest means no running, no rough play, no long walks. For high-energy dogs, this often means crate rest and leash-only bathroom breaks. Some owners invest in calming supplements or additional vet visits to manage anxiety during this period, which can add modest costs. After treatment is complete, your vet will retest for heartworm, typically six to nine months later, to confirm the infection has cleared. If the test is still positive, a second round of treatment may be needed: another course of doxycycline ($30 to $150) followed by two more injections ($500 to $1,000).
Severe Cases and Surgical Costs
Dogs with advanced heartworm disease face higher bills. When the worm burden is heavy enough to physically obstruct blood flow through the heart, a condition called caval syndrome, surgery to manually extract the worms is the only option. This procedure costs $3,000 to $6,000. Dogs in this situation are often critically ill, so emergency stabilization, oxygen support, and extended hospitalization drive the total even higher. Fortunately, caval syndrome is relatively uncommon and mostly occurs in dogs that have been infected for a long time without treatment.
Why Dog Size Matters So Much
Nearly every component of heartworm treatment scales with your dog’s weight. Larger dogs need more medication at every stage: higher doses of the antibiotic, more of the steroid, and larger volumes of the injection drug. The injection medication is priced per vial, and a giant breed dog may require multiple vials per injection where a small dog needs a fraction of one. This is why total treatment costs for a Chihuahua might land around $1,000 while a Great Dane could easily exceed $2,500 for the same protocol.
How Prevention Compares
Monthly heartworm prevention costs roughly $5 to $20 per dose depending on your dog’s size, which works out to $60 to $240 per year. Even at the high end, a full year of prevention costs less than the diagnostic workup alone for a positive dog. Over a dog’s lifetime, prevention runs a fraction of what a single round of treatment costs, and it avoids the weeks of enforced rest, the pain of intramuscular injections, and the risk of potentially life-threatening complications during treatment.