Metformin for the Prevention of Diabetes

Metformin is a drug which is widely used to treat type 2 diabetes (DM2).  In addition, metformin helps prevent DM2, especially when given to patients who have obesity or borderline high HbA1C levels. 

HbA1C is a blood test which is used to diagnose DM and indicates average blood glucose levels.  The higher the glucose level, the higher the HbA1C.  Normal HbA1C is less than 5.6, borderline DM2 is 5.6 – 6.4 and diabetes is diagnosed when HbA1C is greater than or equal to 6.5.

For patients with obesity, a family history of DM2 or borderline HbA1C levels, metformin should be more widely used for the prevention of DM and should be combined with diet and exercise.  In the Diabetes Prevention Trial, intensive lifestyle intervention (diet and exercise) and metformin decreased the risk of DM by 58% and 32%, respectively.  So metformin alone, even without diet and exercise, also helped decrease the risk of DM2.

Also, women with a history of gestational diabetes, DM2 developing during pregnancy (GDM), have a high risk of subsequently developing DM after childbirth, and metformin decreases this risk.

Metformin is a safe drug, but can cause gastrointestinal upset, particularly diarrhea, and over a long period of time, can cause vitamin B12 deficiency.  Vitamin B12 levels should be checked after patients have been taking metformin for over six to twelve months.  Still, most patients tolerate the drug well and obtain substantial benefits from taking it.