Metformin

metformin

A biguanide with metabolic effects and a hypothesised geroprotective action.

TypePrescription drug

⚠ Prescription drug — use only under medical supervision

The grade answers: What does the human evidence support for: Insulin sensitivity / metabolism?

Structure · PubChem

Grade

Moderate

The grade rates evidence quality — it is not advice to take or buy.

Class: Glucose metabolism
Primary use: Insulin sensitivity / metabolism
Evidence strength: medium
Last reviewed: 2025-09-01

Prescription only

Available only on prescription. This entry is informational: we do not point to where to buy it and do not suggest a use.

Bottom line

Decades of proof in diabetes; the anti-aging promise in healthy people is still an unfinished experiment. The dedicated trial (TAME) hasn't reported, so the geroprotective case in humans is unproven.

What the evidence says

Metformin is one of the best-studied drugs in medicine and clearly reduces cardiometabolic risk in type 2 diabetes. The longevity interest comes from observational signals and mechanism, not from a completed aging trial. The TAME trial (Targeting Aging with Metformin) was designed precisely to test whether it delays age-related disease in non-diabetics — until it reports, the geroprotective claim stays a hypothesis, which is why this sits at grade B rather than higher.

Key studies

[1]
Metformin as a tool to target aging — rationale (review) · review
The framework and rationale behind testing metformin as a geroprotector.
Open on PubMed ↗
[2]
TAME — Targeting Aging with Metformin (trial design) · trial protocol
The RCT built to test the aging hypothesis directly; results still pending.
Open on PubMed ↗
[3]
Metformin, exercise adaptation and healthy adults · RCT
A caution: in some studies metformin blunted exercise-training gains — benefit isn't guaranteed in the healthy.
Open on PubMed ↗

See all studies on PubMed ↗

Scoped PubMed search, not a curated bibliography: the individual PMIDs for this entry have not yet been verified one by one. For that reason it is not used to support a high grade and is awaiting review.

Mechanism

Activates AMPK and reduces hepatic gluconeogenesis, lowering glucose and insulin. Proposed geroprotective routes include mild inhibition of mitochondrial complex I, reduced mTOR signalling, lower chronic inflammation and effects on the gut microbiome.

Safety

A prescription drug with a long, well-mapped safety record. The most common issue is gastrointestinal upset (dose-dependent, often transient); lactic acidosis is rare and mostly tied to kidney impairment. Can lower vitamin B12 over time. Not a benign 'anyone can take it' supplement — dosing and monitoring are clinical decisions.

Dosage context

Standard clinical dosing exists for diabetes (typically titrated to tolerance). There is no validated longevity dose or protocol for people without a metabolic indication; that question is exactly what dedicated trials are meant to answer.

Examples of application

A prescription drug dosed and monitored by a doctor.
In the aging context, studied in the TAME trial rather than self-use.
Not a casual 'longevity pill' — clinical indication comes first.

From the field

We keep the grade at B on purpose. Metformin is a genuinely good drug for the right patient, but the longevity story is sold ahead of the evidence. We move the grade when TAME gives us human data, not before.

Related molecules

RapamycinA

Follow this entry

We'll tell you if the grade for Metformin changes.

One review a week: new evidence, grade changes and what was updated. No hype, no promotions disguised as news.

How we assign grades → Method