It depends on how far along the heart worms have become, size and age of the dog. $300-$600 on average, I have a rednose pitbull and he was built like a rhino, mouth like a gator, and could run like a deer, he was positive and the meds ended up giving him a stroke, now he has trouble just walking, as one side is really weak. I hope yours fairs much better, but it's tough, and heart worms and parvovirus has to be the worst things for dogs.