“Metformin slows aging in healthy people.”
Limited confidence because animal, mechanistic and diabetes data do not establish slowed aging in healthy people. A contemporary critical review found that early supportive observational findings have important bias and replication problems, and most trials in people without diabetes have not shown the anticipated broad benefits.
We do not know that metformin slows aging in healthy people. It is an effective diabetes medicine, but human longevity claims rely mainly on indirect, observational and preclinical evidence rather than a completed trial showing slower aging in healthy adults.
Benefits in people with diabetes or high diabetes risk cannot automatically be transferred to metabolically healthy people. Some trials also suggest metformin can reduce selected exercise-training adaptations in older adults.
Safety note: Common effects include nausea, diarrhea and other gastrointestinal symptoms. Longer use can lower vitamin B12, dosing depends on kidney function, and rare lactic acidosis risk rises in specific high-risk settings.
Talk to a healthcare professional if: Metformin for diabetes or selected high-risk prediabetes is a different decision from off-label longevity use. A prescriber should review kidney function, B12 risk, other conditions and the reason for treatment.
A long safety history for an approved indication does not prove net benefit for a healthy person taking it for longevity.
Do not use metformin as a self-directed anti-aging supplement. If you have a metabolic indication, discuss its established benefits and monitoring with your clinician.