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.
Can you give heartworm medicine late?
A: Give the dose you missed immediately, then continue giving the medication on the day you've always given it. If the missed dose is more than 2 weeks late, your dog should be tested for heartworm again in six months (click here to learn why).
What happens if you skip a month of Heartgard?
If it has been less than two weeks since the missed dose, give your dog the dose immediately. If it has been over two weeks since the missed dose, contact your vet, who will likely advise you to resume normal dosing next month and have the dog tested for heartworm in six months.
How late can you give Heartgard?
Monthly heartworm medications can be given one week late without causing any increased heartworm risk. Many experts believe that the medications actually can be given two weeks late without leading to increased risk of infestation, but in my opinion that is pushing things just a bit.
Does Heartgard have a grace period?
When replacing another heartworm preventive in a heartworm disease preventive program, the first dose of HEARTGARD must be given within a month (30 days) after the last dose of the former medication. If the interval between doses exceeds a month (30 days), the efficacy of ivermectin can be reduced.
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