I've been on Victoza for more than 2 years now, and do get bouts of diarhhoea fairly frequently. But I'm also still on Metformin which I never tolerated well, and I put the trots down to the Met. (Also on Gliclazide, but I don't think I'ver ever had side effects from that.
I happen to be on twelve different drugs for various conditions, only three of them for diabetes; with that cocktail of chemicals in my bloodstream I've become resigned to a dodgy digestion, and now regard it as normal.