Nope. We always used the human form. Is your Vet selling you the dog stuff? If so....she's/he's making a profit on it. Probably a much bigger one than say, Amazon would make.
I got my first bottle of Gycoflex III from the Vet. Then for the subsequent one (I only used two bottles worth...prefer the powder I linked above), I went to Amazon. Amazon was just about half price. I buy NOTHING at the Vet unless I need it that very second. Even prescription meds. If I DO need it right then I'll get enough to last me a day or two and ask for an Rx for the others. A lot of meds have a human equivalent. Cephalexin is cephalexin, period. Same thing with Pred, Amoxi, Doxy, etc. And it's a fraction of the cost at places like WalMart. However, there are some meds, like Augmentin (human name)/Clavamox (dog version) is about the same price no matter where you get it. You just have to check around before purchasing from the Vet.
Yes, you're cutting their profits, and if you really love your Vet and have ONE or maybe TWO dogs...then you might be willing to eat the difference. But when I can get 60 capsules of Cephalexin for $10 versus $50...I'll go with the cheaper price.