I order my heartworm meds online, which saves money, but I still have to have my dog checked at the vet before they will send any meds out.
I was in Petsmart the other day and I saw heartworm medication, with the label, for vetinary use only. Don't know why they're selling it. But you can purchase it and show it to your Vet.
Also, Check out Care Credit.Com. You may qualify for their services...It's a Low Income Credit Card used specifically for Animal & Human medical expenses...You can apply online...It wouldn't hurt! They are very low interest & alot of Vet Clinics and Hospitals accept it as a form of payment......Good luck....Karla