Treating Prediabetes with Metformin: A Systematic Review Meta-Analysis

The review of studies was done to determine if the use of metformin in people with prediabetes (impaired glucose tolerance or impaired fasting glucose) would prevent or delay the onset of frank Type 2 diabetes.

Medline was searched from January 1966 to the present, and articles meeting the selection criteria were hand searched. Randomized controlled trials that involved administration of metformin to delay or prevent Type 2 diabetes in individuals with impaired glucose tolerance or impaired fasting glucose were included.

Development of diabetes was a required outcome measure; follow-up time of at least 6 months was required. Three studies met these criteria.

The three studies varied in the ethnicity of the population studied, in the rates of conversion to diabetes from prediabetes, and in the dose of metformin used. In general, the studies were well done, although two of the three did not do true intention-to-treat analyses. A sensitivity analysis was completed by converting all data to intention-to-treat data and assuming a worst-case scenario for the people who were lost to follow-up.

From the meta-analysis it was concluded that metformin decreases the rate of conversion from prediabetes to diabetes. This was true at higher dosage (850 mg twice daily) and lower dosage (250 mg twice or 3 times daily); in people of varied ethnicity; and even when a sensitivity analysis was applied to the data. The number needed to treat was between 7 and 14 for treatment over a 3-year period.

Can Fam Physician. 2009 Apr;55(4):363-9.