We share similar histories. I do not have diabetes, but like you and many, many, many others I have a history of other than
normal blood sugars. Although strongly associated with inflammatory processes, the etiology of pre-diabetes is usually unclear, and by no means does it inevitably progress to full-blown diagnosed diabetes. In fact only about 35-40% of those with prediabetes will do so. But you are still right to be concerned. While the majority of pre-diabetics do not progress to diabetes, pre-diabetes is
not a benign condition. Pre-diabetics, e.g., experience serious cardiovascular events (stroke and heart attacks) at
significantly higher rates than those with normal blood sugars.
Berberine is not something to fool around with. It does seem to work to some degree, but it may do so by
affecting your liver in potentially dangerous ways. It has not undergone the rigorous testing process to which all FDA-approved prescription drugs are subjected, and my view is that it currently should not be prescribed for the treatment of diabetes or pre-diabetes.
Metformin is a good drug with a good track record. It has been around for many decades and is generally very well-tolerated with almost no serious side effects noted except for the rare possibility of lactic acidosis in those with existing kidney disease. Metformin has occasionally been linked in the literature to a decrease in serum Vitamin B-12, so one might want to have that tested when starting metformin to have a baseline (and perhaps take a low-dose B-complex vitamin or multivitamin with Bs if you don't already; high doses of B-12 probably aren't indicated).
I am on metformin and it enabled me to achieve basically normal blood sugars. You may want to consider discussing this with a doctor with experience in the treatment of pre-diabetes and diabetes. For further general information and discussions of treatment protocols for pre-diabetes, see
this site and Dr. Richard Bernstein's seminal book on the subject,
Diabetes Solution.
You should consult your doctor before taking any medication, including metformin.