Review Maps Metformin’s Potential Effects on Aging Across Species

A new review is bringing together decades of research on metformin and aging, while highlighting the substantial gap between promising biological signals and evidence that the drug can extend healthy human life.

Published in Aging, the review examined findings from cellular and molecular experiments, animal studies and human research. The authors propose that metformin may influence several processes associated with aging, including cellular waste clearance, DNA regulation, metabolism and gut-microbiome activity. They describe the drug as a potential geroprotective agent—a compound that might help protect against age-related biological deterioration.

Metformin is widely prescribed for type 2 diabetes, where it lowers blood sugar and improves the body’s response to insulin. According to the review, the drug appears to create a cellular signal resembling an energy shortage, activating AMPK, an energy-sensing pathway involved in cellular maintenance and repair.

The review reports effects across several research models. In C. elegans worms, metformin extended lifespan by 36% to 40%. Across mouse models, the reported increase in average lifespan ranged from 5.8% to 20.1%, and the drug delayed the development of certain tumors. These are preclinical findings and do not establish that metformin extends human lifespan.

The authors also discuss a 40-month study in male monkeys in which treated animals showed younger biological-age measures in their tissues. The review reports that the monkeys’ brains appeared nearly six years biologically younger, a result the article described as equivalent to 18 human years. In people, observational data included in the review associated metformin use with biological ages up to 3.43 years younger. Among people with diabetes, metformin use was also associated with living as much as 15% longer than peers without diabetes.

Those human findings are observational, meaning they can identify relationships but cannot demonstrate that metformin caused the differences. Most human research has involved people with diabetes, making it difficult to separate any effect of the drug from effects related to the underlying disease or other differences between groups.

The review describes several possible biological pathways. Metformin may activate autophagy, a cellular cleanup process, and may help maintain DNA stability. It may also influence DNA methylation—chemical tags that affect gene regulation—by stabilizing the enzyme TET2. In the gut, the authors report that metformin can promote beneficial mucus-protecting bacteria and short-chain fatty acid production.

However, the evidence remains inconsistent. The review notes that cell, animal and human studies have produced mixed findings, and that a widely publicized human survival analysis has faced criticism after other researchers were unable to reproduce its results.

The researchers identify large, rigorous trials in healthy adults without diabetes as the field’s most important missing evidence. They point to the Targeting Aging with Metformin, or TAME, trial as a study intended to test whether metformin can delay the onset of multiple age-related chronic diseases. Until such research provides clearer results, the review supports metformin as a subject of aging research—not as a proven longevity treatment.