For several decades now, one medication has been the primary drug used to treat type 2 diabetes, but research shows there’s still a lot we can learn about how it works inside the body.

Metformin, the second most commonly prescribed medication in the US in 2023, was first synthesized by scientists in 1922 and has been widely used to treat type 2 diabetes since the mid-20th century.

During that time, metformin has been well known for its strong glucose-lowering effects. But a study published in 2025 in Science Advances revealed the drug also affects a part of the body we had never realized – the brain.