Metformin side effects, how long do they last?

MAYBE indefinitely. Metformin has G.I. Side effects including diarrhea and abdominal cramps. The symptoms may last as long as you are taking the medication. One solution is generic glucophage xr or er which is a long-acting medication with less side effects. Many patients can not tolerate metformin at any dose but fortunately we have many diabetes meds --out there. Hope you are better soon!