When to Put Puppies on Heartworm Preventive

If he's old enough to be adopted, he's probably old enough for a heartworm preventative.
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Heartworms spread to your furry friend when he gets a bite from an infected mosquito. The infestation affects your puppy’s heart as well as his lungs; if left untreated, an infestation can be fatal. Treating your pup is far more difficult than preventing the problem to begin with. You’ll need to get your puppy started on a heartworm preventative at just the right age, under the supervision of your veterinarian.

Proper Age

You can start your pint-size chum on a heartworm prevention regime as young as 4 to 8 weeks of age, the American Heartworm Society states. The exact starting age depends on the manufacturer’s instructions for the particular brand your vet recommends.


The majority of heartworm preventative medications available in the United States are designed for monthly use. This means that, once you start, you’ll give your pooch his treatment every 30 days.



Getting your puppy on a heartworm preventative is critical if you live in an area where mosquitoes are prevalent. Humid climates and standing water promote mosquito breeding. If these conditions apply to you, talk with your vet about heartworm prevention right away.