In 2006 the American Diabetes Association recommended it as the first drug of choice for patients, edging out sulfonylureas, a class of drug used since the 1950s that is more likely to cause weight gain and hypoglycemia.
A recent study in the Annals of Internal Medicine showed that metformin gets the job done. Using data from 216 previous controlled trials studies and two reviews, researchers at Johns Hopkins University in Baltimore compared the benefits and risks of various oral diabetes medications.
The only real downside in the study was that metformin was linked with a higher rate of gastrointestinal problems, including gas, nausea, vomiting, and abdominal pain. Many people, though, do just fine or adjust to the drug with time.