When can my puppy have its first dose of Heartgard/Frontline Plus?
Heartgard can be given as soon as he has been tested for existing heartworm infection. Typically this is done at 6-8 weeks of age. Once the results have come back negative, it is safe to begin administering Heartgard Plus once a month. Frontline can be applied starting at 8 weeks of age, regardless of weight, as long as the appropriate weight class is purchased. (eg: Dogs up to 25 lbs.