When I was first diagnosed, I was started on Metformin 250 mg for a week then increased to 500 mg which I took for 4 days then had to stop. It triggered a wicked migraine which lasted for 4 days, bloating, and a feeling that I wanted to go to the toilet but nothing happened when I went. Finally I stopped it and things settled within 2 days. I am now on Glumetza 1000 mg daily (slow release Metformin) which works. It seems that as Metformin is the first line of medications used for diabetics that is what they like to use. I had a very difficult time convincing my physician that Metformin was the cause for my symptoms. I have also tried other medications which include Metformin such as Janumet, and had similar symptoms. I refuse to go on Metformin.