Heartgard Dosages for Dogs

Heartgard is a chewable once-a-month heartworm preventative manufactured by Merial Limited. The ivermectin-based preventative is available in a basic and plus formula that is appropriate for use in dogs that have recently tested negative for heartworm disease. The canine formulas are based on the current weight of your dog and should not be given to animals of other species or to breeds known to have an intolerance of the ingredients.

  1. Heartgard Blue

    • Give one blue-coded tablet once a month to small breed dogs.

      Heartgard and Heartgard Plus in the blue package are for heartworm negative dogs that weigh less than 25 lb. Both the foil that seals the back of the tablet in the plastic container and the box for this weight formula are blue. The dosage is one tablet per month for dogs within the weight range for the blue formula. Each tablet of the basic formula contains 68 mcg of invermectin, while the Plus formula contains 68 mcg of ivermectin and 57 mg of pyrantel.

    Heartgard Green

    • The green box holds Heartgard formulas suitable for medium dogs.

      The green formula is for heartworm negative dogs that currently weigh between 26 and 50 lb. The dosage is one tablet per month for the chewable tablets that can be found in the green color-coded box with green foil. The basic formula for this weight contains 136 mcg of ivermectin, and the Plus formula adds 144 mg of pyrantel to 136 mcg of ivermectin.

    Heartgard Brown

    • This St. Bernard pup would take Heartgard appropriate for his current weight.

      Heartgard and Heartgard Plus in the all brown packaging are for larger dogs that weigh between 51 and 100 lb. The dosage is one tablet per month. Ivermectin contained in the regular formula is 272 mcg, and the Plus contains the same amount of invermectin added to 227 mg of pyrantel.