I was sure I'd read something about Type 1 and Metformin, so I put 'insulin and Metformin in Type 1' into Google, and quite a few articles popped up. The theory seems to be that it'll reduce insulin doses, and possibly help with Dawn Phenomenon, because it inhibits the liver from releasing glucose. My worry would be that, if I'm hypo, and beyond treating it myself, I would need my liver to release some glucose.