Your dog will need to be tested with a simple blood test for heartworm disease on an annual basis. Dogs could get sick (vomiting, diarrhea, and/or death) if placed on heartworm prevention when they have heartworm disease. Even if they have been on heartworm prevention year round there is always the possibility that the product may have failed for various reasons (your pet spit out the pill, did not absorb the pill appropriately, topical medicine was not applied properly, forgot to administer medication on time, etc.) and the earlier we can treat your pet for heartworm disease the better the prognosis. Some companies will guarantee their product providing you use the heartworm prevention year round and are performing yearly heartworm tests. When starting heartworm prevention it is important that you perform an initial heartworm test.
