Hi Rosie, as has already been pointed out tiredness can be a symptom of high blood sugar. Did you take the Metformin after meals? Doing that lessens the side effects for me. How long did you give it before stopping? My side effects haven't quite disappeared (I'm still a bit windy) but I can live with that (I live alone, thank goodness). It was prescribed to help you control your blood sugar, so if you can't tolerate it your GP may prescribe something else. Have you told him/her about the problems?