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.
Metformin has been used outside its official indication of type 2 diabetes for many years. Recognised applications include prediabetes, polycystic ovary syndrome (PCOS, a hormonal condition in women), gestational diabetes, and as a supplement in type 1 diabetes. Much of this use is 'off-label', meaning the drug has not been officially approved for those purposes, and part of the supporting evidence comes from older studies.
In overweight people without diabetes, a study of 154 participants showed an average weight loss of 5.8 kg after six months. The untreated control group had actually gained 0.8 kg. The effect was greater in people with strong insulin resistance, and was independent of age or sex. In prediabetes, there are indications that metformin can delay the progression to full-blown diabetes by improving insulin sensitivity.
Regarding cancer prevention, there is preliminary evidence that metformin may reduce the risk of breast, colorectal, prostate and uterine cancer. However, these are observational studies; it remains unclear whether the effect also applies to people without diabetes, and no recommendation outside a study setting has been made. As for brain function, early research in humans and animal models suggests possible protection against memory decline and Alzheimer's disease, but that evidence is thin.
Whether metformin slows ageing in healthy people remains unanswered. Large clinical trials are currently under way in the United States specifically to investigate this, but results from randomised trials in healthy older adults are still lacking. Long-term use appears to cause few serious side effects, although one known drawback is that it can reduce the absorption of vitamin B12. One important caveat: in fatty liver disease (NAFLD), metformin is now discouraged, because more recent research suggests it may worsen inflammation in the liver. Furthermore, the drug enters the environment via urine, which has been linked to hormonal disruption in fish, and there are questions about effects on human fertility with widespread use.
Evidence comes from a meta-analysis, multiple reviews, and one study that is not further indexed (n=154). Randomised trials in healthy older adults or people without any metabolic condition are still lacking for most applications. Much of the use is observational or off-label.
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 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 has not yet been proven. Wait for the results of the TAME study before drawing conclusions.
What do we really know about metformin and ageing?
Metformin may extend your healthy years by helping to prevent disease, from diabetes to heart and vascular disease. Whether it also slows ageing itself in people without diabetes is for the TAME trial to show, the first large study to test that directly. If you are considering it for that reason, expect stomach and bowel complaints and a falling folate level.
Is berberine safe if you are taking medication?
Berberine inhibits liver enzymes that break down many medications, which can cause blood levels to shift. Do not combine it with medications without thought: always discuss it with your doctor or pharmacist, particularly if you are taking antidepressants, beta-blockers, statins, or blood pressure-lowering medications.
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.
Does metformin lower your risk of cancer or dementia?
In people with diabetes there are indications that metformin lowers overall cancer risk, but the evidence varies or is absent depending on the specific cancer type. Based on the available studies, no conclusions whatsoever can be drawn regarding dementia.