Effect of metformin on patients with impaired glucose tolerance

Diabet Med. 1999 Jun;16(6):477-81. doi: 10.1046/j.1464-5491.1999.00090.x.


Aims: To evaluate the effect of metformin on glucose metabolism, insulin sensitivity and rate of conversion diabetes in people with impaired glucose tolerance (IGT).

Methods: Seventy subjects with IGT were randomized under double-blind conditions to receive either placebo (n = 37) or metformin (n = 33) at a dosage of 250 mg three times daily for a duration of 12 months. Glycaemic control, plasma insulin and other biochemical indexes were assessed before and after 3, 6 and 12 months.

Result: At 12 months the conversion rate to diabetes was 16.2% in the placebo group compared to 3.0% for the metformin group (P = 0.011). Of subjects treated with metformin for 12 months, 84.9% became normoglycaemic compared to 51.4% of those receiving the placebo. Significant improvements in fasting glucose, glucose tolerance and insulin sensitivity were found at 12 months and at intermediate clinic assessments.

Conclusions: Metformin can improve glucose metabolism in IGT patients and may be a treatment option in their management of IGT subjects.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Blood Glucose / metabolism
  • Diabetes Mellitus / prevention & control
  • Double-Blind Method
  • Female
  • Glucose Intolerance / blood
  • Glucose Intolerance / drug therapy*
  • Glucose Tolerance Test
  • Humans
  • Hypoglycemic Agents / therapeutic use*
  • Insulin / blood
  • Male
  • Metformin / therapeutic use*
  • Middle Aged
  • Placebos


  • Blood Glucose
  • Hypoglycemic Agents
  • Insulin
  • Placebos
  • Metformin