By Theo Loxley
Published 27 March 2026  |  TherapyInsights 

A drug prescribed to more than 150 million people worldwide for type 2 diabetes is now being quietly discussed and in some circles, actively taken as a potential anti-aging therapy. But the scientific community is deeply divided on whether the evidence supports the enthusiasm.

Metformin has been in clinical use since the 1950s. It is cheap, widely available, and carries one of the strongest safety records of any medication in existence. In recent years, a series of intriguing findings from primate studies showing slowed biological aging to observational data linking the drug to longer lifespans in diabetic patients has fuelled a surge of interest from researchers, longevity advocates, and the public alike.

Yet a comprehensive review published in Ageing Research Reviews in mid-2025 concluded that metformin has generally failed to demonstrate its anticipated benefits in clinical trials involving non-diabetic populations. The authors described an “emerging uncertainty” around the drug’s anti-aging potential.

So which is it? The answer, as with most things in science, is complicated.

The interest in metformin as a longevity intervention did not emerge from nowhere. It has been building for more than a decade, driven by a convergence of animal research, epidemiological observations, and growing public fascination with the idea that aging itself might be treatable.

The spark came from a widely cited 2014 observational study that found people with type 2 diabetes taking metformin lived longer, on average, than people without diabetes who were taking no medication at all. The finding seemed extraordinary a group with a life-shortening chronic disease outliving the general population and it captured the attention of both researchers and the public.

Since then, metformin has become the drug of choice for a growing community of longevity-focused individuals. Prominent researchers, Silicon Valley executives, and self-described biohackers have publicly disclosed taking it off-label, often at doses of 500 to 1,500 milligrams per day. Online communities trade dosing protocols and tips. Telehealth platforms have emerged that will prescribe it to non-diabetic patients seeking anti-aging benefits.

The scientific interest, meanwhile, is grounded in something more specific: metformin appears to influence several of the fundamental biological processes that drive aging at the cellular level.

Several large observational studies have reported associations between metformin use and reduced mortality, lower cancer incidence, fewer cardiovascular events, and delayed cognitive decline in people with type 2 diabetes.

A 2025 study published in The Journals of Gerontology examined data from the Women’s Health Initiative and found that postmenopausal women with type 2 diabetes who took metformin had a 30 per cent lower risk of dying before the age of 90 compared with women taking sulfonylurea, another common diabetes drug. The authors used age 90 as the threshold for “exceptional longevity.”

A 2024 study published in Cell reported that metformin slowed biological aging clocks in male primates. The drug appeared to reverse several key markers of aging, including a notable 6.1-year regression in brain aging markers. This remains one of the most striking pieces of evidence from animal research.

The Metformin in Longevity Study (MILES), a small randomised trial, reported preliminary findings that metformin induced transcriptional changes in muscle and fat tissue that were consistent with anti-aging effects. While the study was too small to draw definitive conclusions, it provided early human evidence that the drug was doing something beyond lowering blood sugar.

At the cellular level, metformin activates an enzyme called AMPK, which plays a central role in how cells manage energy. This is the same pathway activated by caloric restriction one of the most consistently demonstrated methods of extending lifespan in animal studies.

Metformin also suppresses the mTOR signalling pathway, which is involved in cell growth and has been implicated in aging. It reduces inflammation, limits oxidative stress, promotes DNA repair, and appears to slow cellular senescence the process by which aging cells stop dividing but continue producing inflammatory signals that damage surrounding tissue.

A 2025 study from Baylor College of Medicine added another dimension, revealing that metformin acts directly on a specific brain pathway previously unknown to scientists. As discussed in our analysis of why metformin is being reconsidered as a multi-disease drug, the discovery suggests the drug’s effects on the body are far broader than previously understood.

For all the intriguing findings, a growing body of evidence urges caution.

The most significant critique came from a review published in Ageing Research Reviews in June 2025 by researchers from the University of Southern Denmark, the University of Michigan, and McGill University. The review systematically examined the evidence base and found substantial weaknesses.

The authors noted that the influential 2014 study which found metformin users outliving the general population has faced methodological criticisms and that a subsequent attempt to replicate its findings failed to show the same survival advantage. They also pointed out that metformin has generally not demonstrated significant anti-aging benefits in clinical trials involving people without type 2 diabetes.

A 21-year follow-up of the Diabetes Prevention Program trial, which tracked adults at high risk of diabetes, found that metformin did not reduce rates of cancer, cardiovascular disease, or overall mortality compared with placebo.

The animal evidence is similarly mixed. A critical review published in Frontiers in Endocrinology found that metformin was not consistently associated with lifespan extension in either mice or nematodes when the full body of evidence was considered, despite individual studies reporting positive results.

Some researchers have also raised concerns that metformin may blunt the benefits of exercise a well-established intervention for healthy aging by interfering with mitochondrial adaptations that occur during physical training.

Perhaps most pointedly, one prominent longevity content creator who had publicly championed metformin for years announced in 2024 that he had stopped taking it after reviewing newer evidence, describing the earlier enthusiasm as a case of wanting to believe in a “fountain of youth.”

The contradiction between promising observational data and disappointing trial results is not unusual in medicine, but it does demand explanation.

One key factor is study population. Most of the positive associations come from studies of people with type 2 diabetes a group with elevated inflammation, insulin resistance, and metabolic dysfunction. For these patients, metformin may genuinely improve healthspan by correcting underlying pathology. But whether the same drug offers meaningful benefits to metabolically healthy individuals is a fundamentally different question.

Dose and duration also matter. The primate study that showed biological age reversal used long-term daily administration. Many human trials have been shorter in duration and have used varying dosing protocols, making it difficult to draw consistent conclusions.

There is also the problem of confounding. People who take metformin for diabetes also tend to receive more regular medical monitoring, more lifestyle counselling, and more frequent screening for other conditions. Separating the effects of the drug from the effects of more attentive healthcare is methodologically challenging.

Finally, the definition of “anti-aging” itself is contested. Does it mean living longer? Developing fewer chronic diseases? Maintaining physical function? Slowing biological clocks? Different studies measure different things, and the results depend heavily on which outcome is being assessed.

While scientists debate the evidence, a parallel movement has been growing outside the research establishment.

A growing number of non-diabetic individuals are obtaining metformin prescriptions through their doctors or via telehealth platforms, motivated by the longevity research and the drug’s perceived safety. In the United States alone, more than 91 million metformin prescriptions were written in 2021 a figure that includes both on-label and off-label use.

Prominent figures in the longevity space have disclosed taking metformin, including Harvard geneticist David Sinclair and aging researcher Nir Barzilai, who takes 1,500 milligrams daily. Their public endorsements have influenced a tech-savvy demographic of self-described “optimisers” who view pharmacological intervention as a logical extension of diet, exercise, and data-driven health management.

This trend raises legitimate concerns. While metformin’s safety profile in diabetic patients is well established, long-term use in metabolically healthy individuals has not been rigorously studied. The potential for side effects including gastrointestinal discomfort, vitamin B12 deficiency, and possible interference with exercise adaptations must be weighed against benefits that remain unproven in this population.

No major medical organisation currently recommends metformin for anti-aging purposes. Individuals considering it should do so only under medical supervision.

The most anticipated study is the TAME trial Targeting Aging with Metformin designed by researchers at the Albert Einstein College of Medicine. It would enrol 3,000 adults aged 65 to 79 and track whether metformin delays the onset of cardiovascular disease, cancer, dementia, and death over six years.

TAME is significant not just for its scientific question but for its regulatory implications. If successful, it would be the first trial to establish “aging” as a treatable condition in the eyes of the FDA a paradigm shift that could open the door to an entirely new class of therapies.

However, the trial has been plagued by funding difficulties. As a generic drug with no patent protection, metformin offers no financial return for pharmaceutical sponsors. Estimated costs range from US$45 to $70 million, and as of late 2025, the trial remained only partially funded. Dr Barzilai, the principal investigator, has noted that the TAME framework has already influenced the field Eli Lilly is reportedly designing a similar aging trial using a GLP-1 agonist based on the regulatory template TAME established.

A separate trial the Metformin in Alzheimer’s Dementia Prevention study at Columbia University is also underway, with results expected in 2027. Meanwhile, emerging evidence around metformin’s role in long COVID prevention adds yet another dimension to the drug’s expanding research profile.

The debate over metformin and aging is not merely academic. If even a fraction of the proposed benefits hold up in rigorous trials, the downstream implications for healthcare systems would be considerable.

Chronic age-related diseases cardiovascular disease, diabetes, cancer, and dementia account for the vast majority of healthcare expenditure in developed nations. In Australia, chronic conditions were responsible for 91 per cent of non-fatal disease burden in 2023. The cost of managing these conditions grows as populations age.

A safe, generic medication that could compress the period of age-related morbidity allowing people to remain healthier for longer before experiencing decline would represent one of the most cost-effective public health interventions imaginable. Metformin costs a fraction of newer therapies like GLP-1 receptor agonists, which can run to thousands of dollars per year.

This is the promise that drives the TAME trial: not that metformin will help people live forever, but that it might help them live with fewer years of serious illness at the end of life. For health systems under growing fiscal pressure, that distinction matters enormously.

Australia is ageing rapidly. Adults aged 85 and over represent the fastest-growing demographic segment, and the demand for aged care, disability support, and chronic disease management is rising accordingly.

The National Disability Insurance Scheme supports more than 600,000 participants, many of whom live with age-related or progressive conditions. As the scheme continues to expand, understanding what is funded under the NDIS becomes increasingly important for participants and planners alike.

If interventions like metformin can meaningfully delay cognitive decline, reduce dementia incidence, or compress the period of functional dependency, the downstream effects on both the aged care system and the NDIS could be significant. Fewer years of severe disability means lower lifetime support costs and better quality of life.

Australian policymakers have been slow to engage with the geroscience agenda the idea that targeting the biology of aging could be more effective than treating individual diseases one at a time. As international research accelerates, that gap may become increasingly difficult to justify.

Metformin is not approved anywhere in the world as an anti-aging treatment. It is a prescription medication indicated for type 2 diabetes and, in some jurisdictions, for prediabetes and polycystic ovary syndrome. Any other use is off-label.

The drug’s side effects include gastrointestinal symptoms such as nausea, diarrhoea, and abdominal discomfort, particularly in the early weeks of use. Long-term use is associated with vitamin B12 deficiency, which itself can affect cognitive function an ironic risk for a drug being investigated for brain health. In rare cases, metformin can cause lactic acidosis, though this risk is considered very low in patients with normal kidney function.

There is also emerging evidence that metformin may interfere with some of the physiological adaptations that occur during exercise, potentially blunting the benefits of physical training. For individuals pursuing longevity through a combination of exercise and pharmacology, this is an important consideration.

Patients should not take metformin for anti-aging purposes without consulting a qualified healthcare provider. The evidence is not yet sufficient to support a general recommendation, and individual risk factors must be assessed.

Metformin may influence aging pathways. It is not yet an anti-aging treatment.

The biological plausibility is real. The observational data is suggestive. The primate evidence is striking. But the clinical trial evidence in non-diabetic humans remains thin, and a rigorous 2025 review has highlighted significant weaknesses in the foundational research.

The TAME trial, if and when it is fully funded and completed, could settle the debate or at least move it forward substantially. Until then, metformin occupies an unusual position in medicine: a drug with enormous promise, widespread off-label adoption, and insufficient evidence to confirm that the promise is real.

For a drug that has been in continuous use for nearly seven decades, the most important chapter of its story may still be ahead.

About the Author

Theo Loxley is a healthcare journalist at TherapyInsights covering NDIS, aged care, and the real-world impact of policy on Australian health services.