A You can't use it instead of insulin. Because your pancreas makes little or no insulin, you have to take insulin shots. However, research is now being done on whether metformin, used in addition to insulin, will help certain people with type I diabetes who are being treated with unusually high doses of insulin. This combination treatment should, at this time, be tried only as part of a research study. Therefore, if you have any of those conditions, you shouldn't use metformin.
Some people lose a few pounds when they start taking metformin.
I had a small heart attack. A history of heart attack without heart failure doesn't mean you can't use this drug. I use a sulfonylurea and often have low blood glucose reactions. If that didn't help, switching to metformin may indeed help. When they do this too well, blood glucose levels may go too low.