Meta-analysis: metformin treatment in persons at risk for diabetes mellitus

Am J Med. 2008 Feb;121(2):149-157.e2. doi: 10.1016/j.amjmed.2007.09.016.


Purpose: We performed a meta-analysis of randomized controlled trials to assess the effect of metformin on metabolic parameters and the incidence of new-onset diabetes in persons at risk for diabetes.

Methods: We performed comprehensive English- and non-English-language searches of EMBASE, MEDLINE, and CINAHL databases from 1966 to November of 2006 and scanned selected references. We included randomized trials of at least 8 weeks duration that compared metformin with placebo or no treatment in persons without diabetes and evaluated body mass index, fasting glucose, fasting insulin, calculated insulin resistance, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, and the incidence of new-onset diabetes.

Results: Pooled results of 31 trials with 4570 participants followed for 8267 patient-years showed that metformin reduced body mass index (-5.3%, 95% confidence interval [CI], -6.7--4.0), fasting glucose (-4.5%, CI, -6.0--3.0), fasting insulin (-14.4%, CI, -19.9--8.9), calculated insulin resistance (-22.6%, CI, -27.3--18.0), triglycerides (-5.3%, CI, -10.5--0.03), and low-density lipoprotein cholesterol (-5.6%, CI, -8.3--3.0%), and increased high-density lipoprotein cholesterol (5.0%, CI, 1.6-8.3) compared with placebo or no treatment. The incidence of new-onset diabetes was reduced by 40% (odds ratio 0.6; CI, 0.5-0.8), with an absolute risk reduction of 6% (CI, 4-8) during a mean trial duration of 1.8 years.

Conclusion: Metformin treatment in persons at risk for diabetes improves weight, lipid profiles, and insulin resistance, and reduces new-onset diabetes by 40%. The long-term effect on morbidity and mortality should be assessed in future trials.

Publication types

  • Meta-Analysis
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Adult
  • Blood Glucose / drug effects
  • Body Mass Index
  • Diabetes Mellitus / blood
  • Diabetes Mellitus / epidemiology
  • Diabetes Mellitus / prevention & control*
  • Humans
  • Hypoglycemic Agents / therapeutic use*
  • Insulin Resistance
  • Lipoproteins / blood
  • Lipoproteins / drug effects
  • Metformin / therapeutic use*
  • Middle Aged
  • Prevalence
  • Risk Factors
  • Treatment Outcome


  • Blood Glucose
  • Hypoglycemic Agents
  • Lipoproteins
  • Metformin