I'm on metformin (Glucophage), 1000-1500 mg a day. This is the first time I've been on low carb (tried it 7 years ago for 3-4 months) that I wasn't fighting carb cravings all day, every day. In me, they manifest not only as an intense desire to eat anything with sugar, but with deep, deep depression that comes on so sneakily that I start thinking about death and how great a release that would be and have to really pull myself together and understand that it's not real, just temporary. What a relief the metformin is for me. It prevents the carb cravings and will stop them if I take it after they start and hang in there for just an hour or 2.
I have had a full blood workup and the doctor said my liver, kidney, blood pressure, etc. were "beautiful" so I assume I am not at risk.

I have been trying to wean myself off, but even taking these meds for the rest of my life is preferable to the depression and taking a chance of not having the rest of my life.