According to the International Diabetes Federation, roughly one in nine adults worldwide lives with diabetes, and around 90% of these cases are type 2 diabetes. There is currently no cure for type 2 diabetes. Still, the condition can be managed through healthy lifestyle habits, such as staying active, as well as medication. One widely used medication is metformin, considered a first-line therapy for type 2 diabetes, and it has been prescribed for decades since the Food and Drug Administration (FDA) approved it in 1994. Recent research, however, suggests it may also act directly on the brain, opening the door to new approaches to treatment.Metformin Found to Unexpectedly Affect The BrainScientists at Baylor College of Medicine in the US have discovered a brain pathway that metformin appears to influence, alongside its known effects on other parts of the body. "It has been widely believed that metformin lowers blood sugar mainly by reducing glucose production in the liver. Other studies have also highlighted its action in the gut," says Makoto Fukuda, a pathophysiologist at Baylor. As reported by Science Alert, the researchers explained, "We turned our attention to the brain, given its central role in regulating overall glucose metabolism. Our goal was to understand whether and how the brain contributes to metformin’s anti-diabetic effects."How Is Metformin Affecting Your Brain?Earlier research by some of the same scientists had pinpointed a protein in the brain called Rap1, which influences glucose metabolism, especially in a region called the ventromedial hypothalamus (VMH).In their 2025 study, experiments on mice showed that metformin reaches the VMH, where it helps combat type 2 diabetes by essentially shutting down Rap1. When mice were genetically modified to lack Rap1, metformin no longer affected a diabetes-like condition—even though other medications still worked. This provides strong evidence that metformin acts in the brain through a mechanism distinct from other drugs.The researchers also examined which specific neurons metformin interacts with. This could eventually pave the way for treatments that target these neurons directly. "We found that SF1 neurons are activated when metformin enters the brain, indicating they are directly involved in the drug’s effect," they said.Metformin Side EffectsWhile generally safer than many other type 2 diabetes medications, metformin does have side effects. Gastrointestinal issues such as nausea, diarrhea, and stomach discomfort affect up to 75% of users. Other risks can arise when there are underlying conditions like kidney problems, which may compound health concerns.Metformin is also recognized as a gerotherapeutic—a medication that may slow aging processes in the body. For instance, it has been shown to reduce DNA damage and support gene activity linked to longer life.Previous studies indicate that metformin can also protect the brain from wear and tear and may even lower the risk of long COVID, according to Science Direct.