Every adult dog should have a heartworm test once a year, even on year-round prevention, and before starting or restarting a preventive. Petfolk Veterinary & Urgent Care - Huntersville runs heartworm testing in Huntersville from a few drops of blood in its in-house lab, so most results come back during the visit.
A heartworm test looks back in time: it finds worms from a mosquito bite several months earlier, not last week.
Call (704) 800-4149 or book online.
How long after a mosquito bite will a heartworm test turn positive?
A heartworm test usually turns positive about 5 to 7 months after the infecting bite. Here is the timeline Petfolk Huntersville explains to pet parents:
Day 0, the bite. A mosquito picks up baby worms (microfilariae) from an infected dog, coyote or fox. According to the American Heartworm Society, the larvae need about 10 to 14 days inside the mosquito before its next bite can infect your pet.
The first weeks. Larvae travel through your pet's tissues toward the heart and lungs. No test can find them yet, and this is the stage monthly prevention clears.
About 5 to 7 months. The standard test looks for a protein (antigen) made by adult female worms. That is why a dog bitten in May may test negative in August and positive by winter.
Months to years. Adult worms can live for years in the heart and lung vessels. Later signs include a soft cough, tiring on walks and weight loss.
When should my dog be tested for heartworm?
At Petfolk Huntersville, the American Heartworm Society's schedule is the guide:
Every dog, every 12 months, even on prevention year-round, because doses get missed, spit out or given late.
Adult dogs starting prevention for the first time: test before the first dose and again about six months later.
Puppies: prevention starts young, and the first test usually comes about six months after starting, once a result can mean something.
After a gap: if you missed doses or switched brands, test now and again in about six months.
At Petfolk Huntersville, more than 4 in 10 adult dog wellness visits (43%) include a heartworm test, rising to 46% for dogs 7 and older (Petfolk data, October 2025 to September 2026). Across Petfolk's Charlotte-area clinics, only about 3% of puppy wellness visits include one, which fits the six-month wait above.
What does the heartworm test check?
The heartworm test checks a small blood sample for heartworm antigen. Across Petfolk clinics, the in-house heartworm and tick-borne disease test is the single most-ordered in-house lab test (October 2025 to September 2026). Many in-house heartworm tests also screen for antibodies to some tick-borne infections, such as Lyme disease and ehrlichiosis, from the same drops of blood. For what a full blood panel shows, see our blood work and lab testing page.
How common is heartworm in Mecklenburg County?
In 2025, about 1 in 200 Mecklenburg County dogs tested were positive for heartworm (0.63%), according to the Companion Animal Parasite Council's county map. The AHS notes that infected mosquitoes come indoors, so Petfolk Huntersville tests indoor dogs too. Standing water in yards, ditches and clogged gutters gives mosquitoes room to breed.
How is heartworm testing different for cats?
Testing cats is harder, because cats usually carry only a few worms, sometimes just one, which makes the dog test less reliable. The Petfolk Huntersville vet may combine an antigen test with an antibody test, and sometimes add x-rays or other imaging. Signs in cats can look like asthma: coughing, fast breathing or vomiting. No drug is approved to treat heartworm in cats, so prevention is the only protection.
What happens if my dog's heartworm test is positive?
A positive result at Petfolk Huntersville is confirmed with a second, different test, because treatment is a big commitment. The vet then stages the disease with blood work and chest x-rays and explains treatment options, timing and exercise limits. Don't stop prevention without talking to the vet. You'll get an estimate before anything begins.
Which heartworm signs mean a dog needs care tonight?
A dog with known heartworm that suddenly collapses, has pale gums, struggles to breathe or passes dark, coffee-colored urine needs a 24-hour emergency hospital right away. Those signs can mean worms are blocking blood flow.
Booking a heartworm test with a vet in Huntersville starts with a short visit at Petfolk Veterinary & Urgent Care - Huntersville, 14227 Boren St, Suite 100, Huntersville, NC 28078.
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Heartworm test questions we hear often
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