Out M, et al. - In the HOME trial, a randomized placebo-controlled trial, the researchers examined the effects of metformin, as compared to placebo, on serum levels of vitamin D (25-hydroxyvitamin D [25(OH)D]) in patients with advanced type 2 diabetes. The sample consisted of 390 insulin-treated patients with type 2 diabetes who were treated with 850 mg metformin or placebo thrice daily for 52 months. In patients with type 2 diabetes, metformin had no effect on serum 25(OH)D during 16 months in the setting of a clinical randomized controlled trial. The findings demonstrated that metformin doesn't lead to vitamin D deficiency.