Metformin is the first drug physicians have prescribed for the treatment of diabetes for several decades. It has been the starting point for control of blood sugar levels for millions of patients and forms the foundation of most treatment regimens. Many questions remain, however, about the long term benefits of Metformin such as, compared to placebo:
Does metformin decrease the mortality rate in patients with pre-diabetes?
Does metformin reduce progression to diabetes in patients with pre-diabetes?
Does metformin reduce the rate of cardiovascular deaths?
To get us oriented to what is normal, what is prediabetes, and what is true diabetes, I refer you to the chart in the picture above. Several tests are used as parameters to identify patients that are truly diabetic, pre-diabetic, or not diabetic. These tests are the fasting blood sugar (FBS), the 2-hour post meal blood sugar (2-hr pc BS), the random blood sugar, and the Hemoglobin A1c (HbA1c).
To arrive at an answer to the questions posed above, I refer to an article in American Family Physician, the scientific journal of the American Academy of Family Physicians. Researchers at the Texas Tech University Family Medicine Residency program reviewed 110 scientific studies comparing various treatments for pre-diabetes to placebo. Among those treatment options is metformin and how effective it is in answering the three questions.
Bottom Line: Metformin prescribed to patients with pre-diabetes for prolonged periods of time “DOES NOT decrease the mortality rate in these patients.” It also “DOES NOT reduce the rate of cardiovascular deaths.” It DOES, however, “reduce[s] progression to diabetes.” So if you’ve been on Metformin for a few years for “borderline” blood sugar levels, it may not help you to live longer or keep you from dying from a cardiovascular event, but it will delay you from becoming diabetic by 20%-40%. The specifics of this delay were not reported, but any delay is a good thing.
Reference: Allen C, Barber K, Mallory B, Toti A. Metformin to Decrease Mortality in Patients with Pre-diabetes. Am Fam Phys 2025 July;112(1):79-80.
