Metformin lowers hepatic glucose production and improves insulin sensitivity through several cellular pathways, including effects on mitochondrial energy state and AMP-activated signalling. Those established metabolic actions do not demonstrate slowed aging in people without diabetes.
What it is, why people use it, the evidence, and what to know before trying it.
Regulatory status: prescription-only in the United States and the European Union (and UK/Canada). FDA approved Glucophage 29 December 1994. EMA-authorized Glucophage and generics. There is a US boxed warning for lactic acidosis (see §7). Not OTC. Not a supplement. Gray-market “research chem” metformin is outside every trial cited here.
Mechanism evidence: human
Metformin is a real, cheap, prescription biguanide with **strong** evidence that it lowers HbA1c by about **1 percentage point** in type 2 diabetes and **strong** evidence from DPP/DPPOS that **1,700 mg/day** delayed diabetes by **31%** at 2.8 years and ~**17%** at 21 years in high-risk overweight adults with IGT (**+2.5 years** median diabetes-free). In overweight new-onset T2D, UKPDS 34 and its 10-year legacy follow-up showed fewer diabetes-related events, fewer MIs, and lower all-cause death versus 1990s diet care — a **moderate-to-strong** hard-outcome result **in that disease and era**, not a license for non-diabetic use. **DPP is not TAME.** The same DPP assignment did **not** cut microvascular disease, MACE (HR 1.03), or 2026 Medicare multimorbidity (HR 0.91). **TAME has not launched** (AFAR, August 2026: design ready, donors needed) and has **no efficacy results**. Observational “users outlive non-diabetics” (Bannister) **failed replication** (Keys 2022). Cancer-prevention RCTs are **null**. Weight change is real and small (~**2 kg**). B12 lowering is **established**. Lactic acidosis is **rare** and still **boxed**.
Confidence: strong
Contraindications, interactions and clinical cautions from reviewed sources.
Gastrointestinal effects are common, vitamin B12 can decline with long-term use and rare lactic acidosis is the boxed-warning risk, especially with severe kidney dysfunction, hypoxia or acute illness. Kidney function, contrast procedures, alcohol use and interacting conditions require clinician management. It is prescription-only and should not be started for longevity without a medical indication.
Public protocols that include Metformin (prescription biguanide) — evidence review. Open one to see the full context and source.
Dose and schedule patterns reported in public protocols; these are observations, not prescribing advice. Private and hidden usage is excluded.
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