Caracteristic	HbA1c (%) mean (SD)	Blood glucose mean (SD)	Side effects (%)	Quality of life
Hamilton 2003	At baseline, mean HbA1C% was 9.3 (1.4) vs 8.6 (0.8) in metformin and placebo groups respectively. After 3 months of metformin therapy, change in mean HbA1C was: I: ‐0.3 (0.7)% C: 0.3 (0.7)% P=0.03 At the end of the study, HbA1c was 0.6% lower in the metformin group than in the placebo group (P<0.035)	Mean change of fasting blood glucose after 3 months of metformin therapy I: ‐0.9 (3.8) mmol/l C: ‐0.5 (3.2) mmol/l P=0.04	I: 73% C: 47%	Not reported
Sarnblad 2003	Mean change of HbA1C after 3 months of metformin therapy I: ‐0.9% C: ‐ 0.3% During the study period the mean HbA1c value decreased from 9.6 (1.0) to 8.7 (1.5)% (95% CI for the change: 21.6 to 20.1; P , 0.05) in the metformin group, but remained unchanged (9.5 (1.2) vs 9.2 (1.3)%; ns) in the placebo group	Change in mean glucose concentration during steady state of euglycemic hyperinsulinemic clamp I: unchanged C: unchanged	I: 19% C: 43%	Not reported
Footnotes: Y = yes; N = no; ? = unclear I = intervention; C = control