When I was first diagnosed with type 2 (6 years ago now) I was put onto metformin SR and gliclazide. These did seem to control the sugar levels but I didn't lose any weight. Eventually I was taking 4 metform SR and had really severe diarrhoea, nausea, thirst and headaches (also very tired because I had to keep getting up at night) and this effect didn't wear off. With my doctor's approval, I was taking Immodium every day to try to control it. Then I had to have surgery for bowel cancer and was taken off the metformin "temporarily" and put onto insulin injections. Since then, I was never allowed to come off of the insulin but was kept off the metformin and gliclazide with disastrous effect on my sugar levels.
Last year I was put back on to the metformin and pioglitazone with disastrous effects on my weight as I blew up like a balloon, weighing in at 16.5 stones eventually. I was taken off the pioglitazone but left on the metformin and my 2 insulins - Humilin S and Levemir (total of 118 units in total each day).
I still have trouble with my bowels, but it is less severe now and less frequent, so after a year I seem to be adapting to the medication. It still doesn't work though, and now I have to get rid of all this extra weight. I am currently on 900 cals a day using a full range of food types, but it doesn't work and I still maintain this awful weight. Much against the wishes of my medical advisors, it's heigh ho for a low carb diet for me.
Anyway, metformin is a pain but you can get used to it, even if it takes months, and I suppose it's better than risking the side effects of poor control of sugars - that's if it works at all.