Metformin: The Complete Guide

Metformin (Glucophage) is a biguanide that lowers blood glucose primarily by reducing hepatic glucose production and improving insulin sensitivity. It has been used since the 1950s and remains first-line therapy for type 2 diabetes.

The longevity angle: observational data in diabetics show lower rates of some cancers and cardiovascular events versus other glucose agents. Nir Barzilai's TAME trial proposed testing whether metformin slows aging biomarkers in people without diabetes. That question is still being answered in formal trials — not settled for healthy adults.

AMPK activation: metformin activates AMPK, an energy-sensing pathway also stimulated by exercise and caloric restriction. This overlaps with why biohackers group it with fasting and berberine — but overlap is not equivalence.

Human longevity: no completed large RCT proves metformin extends lifespan in non-diabetic humans. MARS and TAME-era studies focus on composite aging endpoints. MACE and cancer signals come largely from diabetic populations, which confounds 'healthy 40-year-old' extrapolation.

Exercise interaction: some studies suggest metformin may blunt certain mitochondrial adaptations to high-intensity training. If VO₂ max is your north star, discuss timing and necessity with your physician — Attia has raised this tension on air.

Legitimate use starts with indication: prediabetes, insulin resistance, PCOS, or a physician who documents off-label rationale. Baseline labs: HbA1c, fasting insulin, CMP, B12, eGFR. Metformin is contraindicated in severe kidney impairment.

Extended-release formulations often reduce GI side effects. B12 monitoring matters on multi-year use — supplementation is common.

Berberine comparison: Thorne Berberine and similar products hit overlapping pathways for glucose experimentation with a CGM. They are not dose-equivalent substitutes for prescription metformin. Do not swap without medical oversight.

First weeks: nausea, diarrhea, or metallic taste are common; often improve with food timing or XR formulation.

Months in: stable glucose, sometimes modest weight loss. Subjective 'longevity' feelings are unreliable — track labs.

Long term: B12 creep matters. Neuropathy from B12 deficiency mimics other problems — check annually if you stay on it.

Lactic acidosis is rare but serious, especially with kidney disease, heavy alcohol, or acute illness. Hold before contrast CT and surgery per hospital protocols.

GI intolerance drives most discontinuations. Not everyone tolerates it; that is normal.

Do not combine casually with other glucose-lowering agents (including GLP-1s) without endocrine supervision — hypoglycemia risk varies by stack.

r/longevity split: 'wait for TAME' versus 'I'm prediabetic and my doctor already prescribed it.' The middle path — treat insulin resistance seriously, do not treat metformin as a vitamin — is the sensible consensus.

Sinclair association boosted interest; Attia-style skepticism on exercise blunting keeps the conversation honest. Rapamycin and metformin are often discussed as different mTOR/AMPK levers, not a combo to self-stack.