I have heard that it takes four months + for heartworms to form - why is Heartguard given every month? I am concerned because I have a very small dog (under 5 lbs) and don't want to overmedicate.
You are not over medicating and you do not understand the disease. It takes six months for an adult heartworm to develope in the heart in which case no heartworm preventative will help and the damage is alsready done. vetcare