Our study investigated whether metformin has an impact on haemostasis in patients with pre-diabetes receiving statin therapy. The study included 41 simvastatin-treated patients with impaired fasting glucose who were randomized to either metformin (3 g daily) or placebo. The international normalized ratio, the partial thromboplastin time, fibrinogen, factor VII coagulant activity, plasminogen activator inhibitor-1 and von Willebrand factor were assessed on the day of randomization and after 90 days of treatment. Metformin treatment reduced plasma levels/activity of the assessed haemostatic risk factors, and this effect correlated with the improvement in insulin sensitivity. The obtained results indicate that high-dose metformin produces a multi-directional beneficial effect on coagulation and fibrinolysis in patients with impaired fasting glucose already receiving statin therapy. The effect of metformin on haemostasis may play a role in the prevention of atherosclerosis-related disorders and acute vascular events in this pre-diabetic state.