Does metformin help you live longer in good health?
For people with diabetes, metformin has a reasonably well-supported health benefit, but as an anti-ageing agent for healthy people it remains unproven. Wait for the results of that large ongoing study before drawing conclusions.
Metformin has helped people with diabetes for decades: it improves blood sugar levels and sensitivity to insulin, reduces inflammation, and protects blood vessels. As a result, people with diabetes who take metformin live longer and in better health than people with diabetes who do not. That is reasonably well supported. The benefit involves delaying premature death from cardiovascular disease, cognitive decline, and cancer.
The question of whether metformin also works as a life-extending agent for healthy people without disease is an entirely different matter. An early, influential observation appeared to show that people with diabetes taking metformin actually lived longer than healthy people without the condition. That sounds spectacular, but the finding had serious methodological problems and was not confirmed in later studies. That substantially weakens the case for metformin as an anti-ageing agent in healthy people.
In the laboratory and in animals, metformin slows several ageing processes at once. It switches on a kind of energy sensor in cells, slows a growth signal that accelerates ageing, encourages cells to clear out their own waste, and slows the wearing down of chromosome tips. Whether all these effects also occur in healthy people, and whether they actually live longer as a result, has not yet been shown. Early findings from a small study of gene activity suggest that metformin may also influence ageing-related genes in people, but these are preliminary signals only.
A large ongoing study in people is working to answer the definitive question: does metformin slow the development of several age-related diseases at once, in people without diabetes? The results are not yet available. In the meantime, there are two side effects worth taking seriously. Long-term use lowers the absorption of vitamins B12 and B6, with a real risk of deficiencies that should be monitored. There are also signs that metformin may reduce the fitness gains from exercise, which could actually be a drawback for healthy people.
This answer draws on several combined bodies of research, none of which are studies where people were randomly assigned to metformin versus a dummy pill with lifespan as the outcome. The evidence for benefit in diabetes is the strongest. For healthy people there is no convincing evidence: the early observations have been called into question and a large ongoing trial is still running. The cell and animal findings are promising but have not translated into demonstrated benefit for healthy people.
What do we really know about metformin and ageing?
In people with diabetes, metformin shows clear health benefits. Whether it also slows ageing in healthy people is being investigated by an ongoing study.
What are the side effects of metformin?
Metformin causes gastrointestinal complaints such as diarrhoea, nausea and vomiting in a substantial proportion of users. Discuss with your doctor whether the dose can be built up gradually, or consider an alternative if the complaints persist.
Does rapamycin help people live longer in good health?
Rapamycin works in mice, but whether it also leads to a longer and healthier life in humans has not yet been demonstrated. Side effects are real, long-term data in healthy people are absent, and use outside a clinical context cannot currently be justified.
Can you take metformin without having diabetes?
Metformin has a reasonable evidence base for specific groups without diabetes (prediabetes, PCOS, overweight with insulin resistance), but as a general agent for healthy people, evidence from large randomised trials is entirely absent; always discuss use with your doctor.
How does metformin work in your body?
Metformin lowers blood sugar primarily by causing the liver to produce less new glucose, without the risk of dangerously low blood sugar. Exactly how all the pieces of the mechanism fit together is not yet fully clear.
Does metformin help with weight loss?
Metformin helps with weight loss, but the effect is modest: expect a few kilograms, not a dramatic transformation. Lifestyle changes work better in the short term, but weight loss with metformin remains stable over the long term. Discuss it with your doctor if you want to know whether it suits your situation.