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All research profiles

Prescription metabolic / longevity

Metformin

Prepared by the ezGLP team. Sources last checked . Profile reviewed .

Routes represented in the knowledgebase: Oral.

Educational overview

FDA-approved for type 2 diabetes; longevity use in healthy people is off-label and unproven. The label includes a lactic-acidosis boxed warning.

Metformin is an oral biguanide and the most widely prescribed glucose-lowering medicine in the world. Its chemical ancestry runs through galegine, a guanidine compound found in Galega officinalis, and it entered European practice in the late 1950s. It lowers blood glucose mainly by reducing hepatic glucose production and improving peripheral insulin sensitivity, without stimulating insulin secretion, so on its own it rarely causes hypoglycaemia. Proposed mechanisms include partial inhibition of mitochondrial complex I, a shift in cellular energy charge that activates AMP-activated protein kinase, inhibition of mitochondrial glycerophosphate dehydrogenase, and gut-mediated effects on incretin release and bile acids.

The evidence base spans decades. UKPDS 34, published in the Lancet in 1998, followed overweight adults with newly diagnosed type 2 diabetes and reported fewer diabetes-related endpoints and lower all-cause mortality with metformin than with conventional treatment. The Diabetes Prevention Program, published in the New England Journal of Medicine in 2002, randomised 3234 adults with impaired glucose tolerance and reported that metformin reduced progression to type 2 diabetes by about 31 percent relative to placebo, while intensive lifestyle intervention reduced it by about 58 percent. Interest in metformin as a geroprotective agent rests largely on observational data and animal work, summarised in the 2016 proposal for the TAME trial.

Metformin is approved in the United States, the European Union and most other jurisdictions for type 2 diabetes, and it appears on the World Health Organization's list of essential medicines. Formulations include immediate-release and extended-release tablets, an oral solution, and many fixed-dose combinations with other glucose-lowering agents; generics are ubiquitous. The United States label carries a boxed warning for lactic acidosis, a rare but potentially fatal accumulation that becomes likelier when renal clearance falls, and the drug is contraindicated in severe renal impairment. Use for longevity or healthspan in people without diabetes is off-label everywhere and supported by no approval.

Tablets are stored at controlled room temperature per the product label, with no cold chain, and extended-release shells are sometimes passed intact in stool without meaning the drug was not absorbed. Between 2019 and 2021 the FDA reported nitrosamine (NDMA) impurities in some extended-release metformin products and several manufacturers issued recalls, which is one reason the specific manufacturer and lot number matter in a record rather than the ingredient name alone. Because immediate-release, extended-release and fixed-dose combination products differ, an inventory record that captures formulation, strength, manufacturer and lot keeps a dose log matched to what was actually dispensed.

Category
Prescription metabolic / longevity
Routes represented
Oral
Storage context
Follow the product or pharmacy label; requirements vary by route and formulation.
Authoritative overview

Published literature

No verified PubMed or DOI link is available for this entry.

Safety evidence

Common or reported: diarrhea, nausea, vomiting, gas, abdominal discomfort, headache.

Serious or important: lactic acidosis, vitamin B12 deficiency.

Safety evidence source

Interaction evidence

These are general, pairwise evidence notes. Green identifies the potential-synergy category, while Lv3/Lv2/Lv1 communicates evidence strength; it does not guarantee benefit or cancel a safety warning.

With carbonic anhydrase inhibitors

Safety flag

Additive metabolic acidosis can increase metformin-associated lactic-acidosis risk.

Interaction evidence source

With OCT2/MATE inhibitors

Safety flag

Reduced renal metformin clearance can increase exposure and lactic-acidosis risk.

Interaction evidence source

With alcohol

Safety flag

Alcohol potentiates metformin's effect on lactate metabolism and increases lactic-acidosis risk.

Interaction evidence source

With Cyanocobalamin

Safety flag

Long-term metformin use can reduce vitamin B12 absorption and serum B12 concentration.

Interaction evidence source

Common questions

Why does metformin have a boxed warning?

The warning concerns metformin-associated lactic acidosis, an accumulation of lactate that is rare but carries high mortality when it occurs. Metformin is cleared unchanged by the kidneys, so exposure rises when renal function falls, and the label lists severe renal impairment as a contraindication. Conditions that raise the risk include acute kidney injury, hepatic impairment, sepsis, hypoxic states, heavy alcohol intake and iodinated contrast procedures.

Does metformin extend lifespan?

That question is unresolved. Observational analyses have reported lower mortality among people with diabetes on metformin than on some comparators, and animal studies have shown lifespan effects in certain models, but observational data are open to confounding and no randomised trial has tested longevity in people without diabetes. The proposed TAME trial, outlined in 2016, was designed to address the gap and had not reported at this review.

Does metformin cause vitamin B12 deficiency?

Long-term treatment is associated with reduced vitamin B12 absorption and lower serum B12 concentrations, an effect described in the product label and observed in the Diabetes Prevention Program's long-term follow-up. The reduction is dose- and duration-related. Because B12 deficiency can produce anaemia and peripheral neuropathy that overlap with diabetic neuropathy, labels describe periodic measurement of B12 during prolonged treatment.

What is the difference between metformin and metformin ER?

They contain the same active ingredient in different delivery systems. Immediate-release tablets release metformin rapidly and are taken more than once a day, while extended-release tablets use a matrix that releases the drug over several hours from a single daily administration. Trials report broadly similar glycaemic effects, with gastrointestinal complaints often described as less pronounced with the extended-release form.

Is metformin approved for weight loss?

No. Metformin's approved indication is glycaemic control in type 2 diabetes, not weight management, in the United States, the European Union and comparable jurisdictions. Trials including the Diabetes Prevention Program recorded modest weight reduction of a few kilograms on average, considerably smaller than that seen with incretin-based medicines. Prescribing it for weight loss alone is an off-label practice rather than an approved indication.

Further reading

Summarised from published literature for reference only, with citations to the source. Evidence is graded as reported and is not a recommendation to combine, dose, or use any compound.

For personal tracking and education only. Not medical advice, diagnosis, or treatment, and not a medical device. Peptides may be prescription-only or unapproved where you live. Consult a licensed healthcare professional.