Metformin has a strange history. There was evidence in animal studies as early as the 1920’s that it could lower blood sugar, but wasn’t approved as a diabetic treatment until the 50’s. The US didn’t approve it until the 90’s.

It’s still not clear how it works. There continue to be articles like this hinting that it could have other beneficial effects, including a lower incidence of cancer and longer life, which again no one can explain how. All the research pointing at other effects besides blood sugar are observational and longitudinal in nature.

Lest someone think it’s a wonder drug, all these effects are relatively subtle, and side effects for many include things like explosive diarrhea.