I've had a good experience with Metformin for the month I have been taking it ( 500x2). It and a modified diet have reduced Bg significantly. I had no significant side effects until tonight, shortly after my 2 hour PP test, when with one severe stomach cramp and about 10 seconds warning, terrible diarrhea. I probably posted a world class time ( for senior citizens) for the 20 metre dash to just make it to the loo. I thought that the gastric issues with Metformin mostly came at the commencement of treatment or following an increase in dose? Can it have this effect with sudden onset well into treatment? The lack of warning of this episode was quite disturbing. I hope it is not indicative of what might happen in the future .