Metformin
A drug from another class of medications, metformin, works three ways: It lowers the amount of glucose produced in the liver, increases the uptake of glucose by the muscles, and improves the body's resistance to insulin. The side effects of this medication are mainly gastrointestinal, such as diarrhea, nausea, and vomiting. The drug also increases risk of heart failure and increases the production of acid. Therefore the drug should not be taken in elderly people or those with impaired kidney function.