I have also heard that chromium picolinate can reduce a person's requirement for sugar-lowering drugs. I don't know how much would be the equivalent of 500mg Glucophage, but I don't believe that this would be one of those do it yourself endeavors. The effective dose of chromium picolinate for a diabetic can be anywhere from 600-1000mcg per day. If you want to try this, however, you really should talk to your doctor about it first.
R-lipoic acid, the natural form of alpha lipoic acid, is also a good supplement for lowering blood sugar. Doses of between 300-900mg have been used for this purpose.
Most recently, I read an article in the newspaper about cinnamon. It said that taking a half teaspoon of cinnamon per day can also help lower blood sugar.