What Is Metformin Used for Other Than Diabetes

What is metformin used for other than diabetes? The most common non-diabetes uses include prediabetes (off-label), polycystic ovary syndrome (off-label), gestational diabetes, weight management as an adjunct, and emerging aging research through the TAME trial. All non-diabetes uses are either off-label or research-stage and require a clinician’s evaluation.

Quick Refresher on Metformin

Metformin is an oral biguanide first introduced in the 1950s and FDA approved in the United States in 1995. Its primary mechanism is to reduce hepatic glucose production through AMPK-related pathways and to modestly improve peripheral insulin sensitivity. It does not stimulate insulin secretion, so it rarely causes hypoglycemia on its own. Most adults tolerate it well, with GI side effects (diarrhea, nausea, abdominal discomfort) being the most common. Extended-release formulations reduce GI symptoms for many patients. For broader context, see our prediabetes treatment overview.

Prediabetes (Off-Label)

Metformin is not FDA approved for prediabetes, but it is widely used off-label based on the landmark Diabetes Prevention Program. Published in the New England Journal of Medicine in 2002, the DPP randomized 3,234 adults with prediabetes to lifestyle intervention, metformin 850 mg twice daily, or placebo. Over 2.8 years:

• Lifestyle intervention reduced progression to type 2 diabetes by 58%
• Metformin reduced progression by 31%

The American Diabetes Association supports considering metformin in adults with prediabetes who are under 60, have BMI 35 or higher, or have a history of gestational diabetes. The 10-year DPP Outcomes Study confirmed sustained benefit. For background, our guide to reversing prediabetes covers the lifestyle pillars that pair with medication.

Polycystic Ovary Syndrome (Off-Label)

PCOS is strongly linked to insulin resistance and is one of the most common off-label uses of metformin. Benefits documented in randomized trials and recommended in international PCOS guidelines include:

• More regular menstrual cycles
• Improved ovulation, sometimes used adjunctively in fertility care
• Modest reduction in androgen levels
• Modest weight reduction in insulin-resistant women
• Improved metabolic markers

Metformin is generally not first-line for cosmetic concerns like hirsutism, where combined oral contraceptives are typically preferred, but it remains a core metabolic option in PCOS care.

Gestational Diabetes

Metformin has been studied as an alternative or adjunct to insulin in gestational diabetes. Randomized trials such as MiG (2008) showed comparable glycemic control to insulin in many women with gestational diabetes, though insulin remains first-line in most United States guidelines. Metformin crosses the placenta, and longer-term outcome data on offspring continue to mature. Use in pregnancy should be a shared decision with an obstetrician or maternal-fetal medicine specialist.

Weight Management Adjunct

Metformin is not FDA approved for chronic weight management, but average weight loss in placebo-controlled trials is modest (typically 2-3 kg). It is sometimes used off-label in adults with obesity, prediabetes, PCOS, or insulin resistance, especially when GLP-1 therapy is unavailable, unaffordable, or not tolerated. Combined use with GLP-1 medications is common in clinical practice.

Antipsychotic-Associated Weight Gain

Metformin has been studied as an adjunct to mitigate weight gain associated with antipsychotic medications such as olanzapine and clozapine. Several randomized trials and meta-analyses suggest modest benefit on weight, BMI, and metabolic markers in this population.

Aging Research: The TAME Trial

The TAME (Targeting Aging with Metformin) trial is a planned multi-center randomized trial designed to test whether metformin can delay the onset of age-related diseases in older adults without diabetes. Mechanistic interest stems from metformin’s effects on AMPK, mTOR, mitochondrial function, and inflammation. Observational data are mixed; randomized trial results are needed before metformin can be recommended as an anti-aging therapy. The TAME trial is one of the first major studies designed to use aging itself as an endpoint.

Other Investigational Areas

• Cancer prevention: Observational studies suggest possible reductions in some cancer types in adults with diabetes; randomized data are limited and inconsistent.
• Non-alcoholic fatty liver disease (NAFLD/MASLD): Modest improvements in liver enzymes, but not consistent histologic improvement.
• Long COVID symptoms: Investigated in trials such as COVID-OUT, with some signal for reduced post-acute symptoms; further confirmation needed.
• Cognitive decline and dementia: Observational signals in adults with diabetes; randomized data limited.

Safety, Contraindications, and Practical Notes

• Most common side effects are GI (diarrhea, nausea, metallic taste), often improved with extended-release formulations and slow titration.
• Vitamin B12 levels may decline with long-term use; periodic monitoring is reasonable.
• Severe kidney impairment (eGFR less than 30) is a contraindication; caution between 30-45.
• Hold around iodinated contrast procedures per institutional guidance.
• Lactic acidosis is rare but serious; risk rises with significant kidney, liver, or cardiac disease.

The Bottom Line

Asking what is metformin used for other than diabetes leads you to a long list of established (PCOS, prediabetes, gestational diabetes, weight management adjunct) and investigational (aging, cancer, NAFLD) uses. Most are off-label, with varying evidence strength. Metformin is a well-studied, low-cost, generally well-tolerated medication, but every non-diabetes use deserves a personal conversation with your clinician.

Medical disclaimer: This article is for educational purposes only and is not medical advice. Always consult your physician or a qualified healthcare provider before starting, stopping, or changing any medication or treatment plan.