Metformin is the cornerstone of treatment early in the course of type 2 diabetes. Recent studies also provide evidence for the benefits of metformin when given late in the course of the disease, after the introduction of insulin.1 2 However, because metformin targets insulin resistance in overweight patients, can it be as beneficial in non-obese patients?

In the linked randomised controlled trial (doi:10.1136/bmj.b4324), Lund and colleagues compare the effects of metformin versus repaglinide in non-obese patients with type 2 diabetes treated with insulin.3 They randomised 102 patients (body mass index ≤27 and glycated haemoglobin ≥6.5), after a run-in period with combined repaglinide and metformin, to receive either repaglinide 6 mg plus insulin or metformin 2000 mg plus insulin. Patients had been known to …