I have been taking Metformin for several years now. I use it with glyburide and now with Avandia as well. I think that Metformin should work quicklly. I first used just exercise and then just glyburide but I had to keep increasing the dosage of glyburide so the doctor used metformin to help out. It worked almost right away. Eventually though after several years even that combination ceased to keep my BG at target levels (below 7 fasting in international units). I started avandia plus metformin but that did not work at all. I changed doctors and the new doctor put me back on glyburide as well. It is working wonders. I think that next time I visit the doctor we can cut down on the avandia dosage at least for a while. I suppose eventually I will go on insulin but I am 74 and have had no complications so I guess I can't complain!