The use of Metformin is associated with better prognosis after stroke.

In "Association of prestroke metformin use, stroke severity, and thrombolysis outcome," Westphal et al. reviewed data from the European Thrombolysis in Ischemic Stroke Patients collaboration and compared stroke severity (NIH Stroke Scale), 3-month functional outcome (modified Rankin score), and mortality in 757 patients with type 2 diabetes who received metformin before stroke and 1,162 patients with type 2 diabetes who did not receive metformin before stroke. The authors reported that patients on metformin had less severe strokes, better functional outcome, and lower mortality and concluded that these findings suggest metformin has a protective effect in this patient population. 

The authors suggested their findings may precipitate additional studies on the relationship between metformin and outcome after stroke and increased use of metformin in patients with diabetes and vascular risk factors.