Most of the monthly heartworm medicines have a safety factor of at least 15 days of protection if a dose is missed. This means that if you're just a week or two late, your pet is likely still within that window of protection and would be unlikely to become infected during that time.
What happens if you forgot to give your dog heartworm medicine?
A dog who has missed just two monthly doses of preventative or is late for a heartworm injection can become infected with heartworms.
How long can a dog Miss heartworm treatment?
The common consensus is that it takes about 40‒50 days for heartworm larvae to mature to the point where heartworm preventatives no longer work. So, from the initial mosquito bite to the beginning of maturation, there is an approximate 45-day grace period that a heartworm preventative can provide protection.
What happens if you miss 2 months of heartworm medicine?
I have missed 2 months of heartworm prevention for my dog. What should I do? You need to consult your veterinarian, and immediately re-start your dog on monthly preventive—then retest your dog 6 months later.
Do dogs need to be on heartworm medicine all year?
Yes, your dog needs heartworm medicine year-round. Just because mosquitoes may hibernate in the winter doesn't mean they're gone. And just because you live in a colder state doesn't mean your dog is safe either.
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