Again, we hear this question a lot: My pet is on heartworm prevention every month, why do I need the annual test? We wanted to help provide some basic info to help clarify why we heartworm test and when.
Annual testing is necessary, even when dogs are on heartworm prevention year-round, to ensure that the prevention program is working. Heartworm preventives are highly effective, but not 100 percent effective. If you miss just one dose of a monthly medication—or give it late—it can leave your dog unprotected. Even if you give the medication as recommended, your dog may spit out or vomit a heartworm pill—or rub off a topical medication. There can be lapses in the manufacturing of the medication that effects the efficacy of the drug. Annual testing also protects your pet (and wallet). If your pet tests positive, with proof of continual purchased from an authorized* source and past heartworms test, most manufacturers will help cover the cost of treatment.
When should my pet be tested for heartworms?
All dogs should be tested annually for heartworm infection, and this can usually be done during a routine visit for preventive care. Following are guidelines on testing and timing:
- Puppies under 7 months of age can be started on heartworm prevention without a heartworm test (it takes at least 6 months for a dog to test positive after it has been infected).
- Adult dogs over 7 months of age and previously not on a preventive need to be tested prior to starting heartworm prevention. They then need to be tested 6 months after beginning prevention to ensure the initial test wasn’t a false negative. After these initial tests, they are then tested annually as long as they stay current on prevention.
- If there has been a lapse in prevention (one or more late or missed doses), dogs should be tested six months from the first missed dose. (If the pet missed in July and August, we would test in December.) As long as the pet remains current, testing is done annually after that.
*Manufacturer authorized sources are licensed veterinary practices and VIPPS approved online pharmacies (such as our Pet Portal). 1-800 PetMeds, Drs. Fosters & Smith, etc are not manufacturer authorized distributors. Any manufacturer guarantee is null and void through these sources.