Metformin Lengthened Telomeres 29.6% in a Prediabetes Trial
Topics: Biological Age & Clocks
Jeff's Daily Pick. A cheap diabetes pill lengthened the protective caps on chromosomes by 29.6% in six months, versus 4.4% on placebo. Here is what that number does and doesn't mean.
In India, researchers at the Fortis C DOC Centre of Excellence for Diabetes in New Delhi randomized 127 adults aged 30 to 60 with prediabetes to metformin or placebo for 24 weeks. The trial, published online on September 3, 2026 in Mechanisms of Ageing and Development, reports that metformin lengthened leukocyte telomeres, the protective caps at the ends of chromosomes in white blood cells.
The trial
Participants received metformin 500 mg twice daily (63 people) or placebo (64), plus lifestyle counselling for both groups; 112 completed the study, 56 per arm. Participants and outcome assessors were blinded. The primary outcomes were measured in blood cells by quantitative PCR: telomere length, telomerase activity, and the expression of four genes linked to longevity pathways, SIRT1, p66Shc, p53 and mTOR. The trial is registered as NCT07302932.
The numbers
Telomere length rose by 0.247 (standard deviation 0.298) on metformin against 0.036 (0.068) on placebo, reported as 29.6% versus 4.4% elongation (between group p < 0.0001). Telomerase activity rose 39.3% on metformin and fell 1.41% on placebo. SIRT1 expression rose 30.41% versus 3.54%. The authors note these changes occurred without major weight loss and independently of blood sugar control.
What it shows / what it doesn't
- Shows: in a randomized trial, metformin changed several blood markers associated with cellular aging over six months.
- Shows: the effect on telomere length was large in relative terms and statistically clear.
- Doesn't show: slower aging, fewer diseases or longer life. Telomere length is a surrogate.
- Doesn't show: a reliable measurement. qPCR telomere ratios are noisy, and a 29.6% gain in six months is unusually large for this marker.
- Status: peer reviewed single center trial, 112 completers, participant and assessor blinded.
Where it fits
Metformin's anti aging reputation rests mostly on observational data and lab work, which is why the TAME trial was proposed to test it against diseases of aging as a group. A UK Biobank analysis published in 2023 linked metformin targets to younger phenotypic age but not to telomere length, which shows how inconsistent this marker can be. A replication with a second telomere method, more participants and a longer follow up is the test this result needs. Our explainer on biological age clocks covers why surrogate markers often disagree.
Sources
Peer reviewed randomized controlled trialBhatt SP, Pandey S, Misra A et al. Metformin therapy increases leukocyte telomere length, telomerase activity, and longevity gene expression in Asian Indians with prediabetes. Mech Ageing Dev 2026;234:112241. sciencedirect.com
PubMed record 42692117. pubmed.ncbi.nlm.nih.gov
ClinicalTrials.gov NCT07302932, Metformin and Molecular Aging in Prediabetes. clinicaltrials.gov
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