I got started on metformin a week ago after years of trying to manage on a very restricted diet and 5h cycling/jogging per week. Hb1ac was 5.5, so really still acceptable, but my fasting bg would only go below 120 on low-carb and after losing 16kg on Newcastle Diet over the summer (now BMI 25, same as before having children), and even then I would wake up most nights feeling feverish and having to drink vast amounts of water just to be able to go back to sleep. Just to add to the discussion: no side effects here except for slight bloating. That familiar feverish feeling after eating carbs, no matter how few, the itchy legs and swollen fingers have all gone.