the berberine (which in some studies has worked even better than metformin and, arguably, has fewer side effects, though I think both are good) did lower my fasting glucose and brought down my a1c a bit...I am going in for as two hour glucose test soon and will see what that says. In general A1c is not as very good test. The latest data indicate that a properly administered fasting 1 hour glucose test finds far more cases of pre-diabetes and diabetes than any of the other tests but it is not so easy to find this test. The glucose load has to be adjusted accordingly, etc. Typically people take 1500 mg of berberine a day in three divided (500 mg) doses. The most reported side effect is constipation which in most cases resolves within a few weeks at most; it did for me.