“Does taking metformin for a long time affect the body?”

Metformin affects the body, but I suppose you mean "does long-term metformin adversely affect the body." The answer to that question is probably no. We have been using metformin in this country for 30 years & in Europe for over 50 years with few adverse effects. Thousands of people have been treated with it for many years safely. The only bad effects are the gastrointestinal effects usually seen for a few weeks at the beginning of therapy then go away and a condition called "lactic acidosis" if given with kidney disease. I have treated thousands of people, many of them for many years, & have seen only 1 case of lactic acidosis. This occurred in a man with kidney failure who should never have been taking metformin. Metformin is not only safe for many years, but some recent data have shown some long-term effects that may be beneficial apart from its effect on blood sugar. There are some preliminary data to suggest that metformin may change gut bacteria for the better helping with some inflammatory diseases. It may also prevent certain cancers such as breast & prostate and some very preliminary data suggests it may slow the development or progression of Alzheimer's disease. These are all preliminary data mainly in animals, but they are certainly exciting. So don't be afraid of long-term metformin. If it is working, keep it going. It is certainly the cheapest med you can take for your diabetes. Above all, take whatever you need to keep your blood sugar & A1c in control. Metformin can be taken with other diabetes meds & may help them so GO FOR IT!