I have been taking Metformin for well over a year now.
Metformin can cause diarrhea in over 50% of people on the med. have you just started this med.? call your doctor
I'm currently taking Metformin, an antidepressant, vitamin D, and birth control.
If you're having diarrhea for over a week you should see a doctor! make sure you drink plenty of water so you don't dehydrate. Are you on any medications?