Adult dogs need a heartworm test once a year, even on year-round prevention, and puppies get their first test at about seven months old. A heartworm test is a small blood sample checked for proteins from adult heartworms. Petfolk SouthPark is a veterinary clinic in Charlotte, North Carolina, that runs the test in its own in-house lab, so many results are ready during the visit; see our vet in SouthPark.
Heartworms are long, thin worms that live in the heart and the large blood vessels of the lungs. A mosquito picks up tiny larvae from an infected dog, coyote or fox and passes them on with its next bite. The American Heartworm Society reported in May 2026 that the disease is most common in warm, humid regions and is spreading into areas once thought rare.
Call (980) 580-8079 or book online.
Why does a dog on prevention still need a yearly heartworm test?
A yearly heartworm test catches infections that slip through, because doses get missed, spat out or vomited and no product is perfect. The American Heartworm Society recommends annual testing for all dogs (AHS heartworm basics). The test also comes before starting or restarting prevention, since giving certain preventives to a dog who already has adult worms can cause a reaction.
How often do SouthPark dogs get tested?
At Petfolk SouthPark, about half of wellness visits for adult dogs include a heartworm test: 52% for dogs 1 to 7 years old and 51% for dogs 7 and older (October 2025 to September 2026). The heartworm screen is also the single most-ordered in-house lab test at Petfolk SouthPark over the same period.
In Mecklenburg County, about 1 in 200 dogs tested were positive for heartworm in 2025 (0.63%, Companion Animal Parasite Council). Low, but not zero, which is why the test stays on the yearly list.
When is the best time of year for a heartworm test in Charlotte?
Any time of year works for a yearly test at Petfolk SouthPark, but knowing Charlotte's mosquito calendar helps you read the result.
January to March. Few mosquitoes, and a good time to test. The test finds adult worms, and larvae picked up last fall take about six months to grow into adults that show up.
April and May. Mosquitoes return as days warm. Charlotte's average first 90-degree day is around May 20 (WBTV weather data). If doses were paused over winter, test before restarting.
June to August. Peak mosquito months. Mecklenburg County Public Health found West Nile virus in a mosquito pool collected July 14, 2026, a different disease carried by the same kind of insect.
September to November. The season doesn't end with Labor Day. WBTV reported that October 15, 2026 was Charlotte's latest 90-degree day on record, and a bite in October can turn into a positive test the next spring.
December. Fewer mosquitoes, but not none on mild days. A good month to check that the next test date is on the calendar.
What happens at a heartworm test at Petfolk SouthPark?
Exam and history. The Petfolk SouthPark doctor examines your dog and asks which prevention product you use and whether any doses were late or missed.
Blood sample. A small sample, usually from a leg vein, takes a few minutes.
In-house screen. The sample is checked for heartworm proteins in the clinic lab; many results are ready before you leave.
Plan. The doctor explains the result and sets the next test date. The blood work page covers other tests that can run from the same visit.
Who should get a heartworm test, and when?
Adult dogs: once a year, even on year-round prevention.
Puppies: prevention starts early, and the first test usually comes around seven months, when a result means something.
Dogs switching products or restarting after a gap: test before the change, then again later.
Cats: cats can get heartworms, but the disease behaves differently and standard tests miss many cases. Ask the Petfolk SouthPark doctor whether testing makes sense for your cat.
What if the heartworm test is positive?
A positive screen at Petfolk SouthPark is usually confirmed with a second, different test. Next steps often include chest x-rays to look at the heart and lungs (see the pet x-rays page) and blood work to check organ health. You get an estimate before any treatment begins. Keep a positive dog calm and on leash while the plan comes together, because exercise can make heart and lung damage worse.
Which heartworm signs mean go to an emergency hospital?
Go to a 24-hour emergency hospital if your dog suddenly collapses, struggles to breathe or coughs up blood; these can occur with severe heartworm disease. Petfolk SouthPark is open 8 AM to 6 PM, seven days a week, and doesn't provide overnight care.
How do I book a heartworm test near Cotswold?
Petfolk Veterinary & Urgent Care - SouthPark, 4914 Old Sardis Rd, Unit C5, Charlotte, NC 28211, is a short drive from Cotswold. Call (980) 580-8079 or book online.
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Heartworm test questions
In Strawberry Hill, near Fairview Road