How does metformin help with PCOS?
Metformin is commonly prescribed to help manage polycystic ovary syndrome (PCOS) because it improves the body’s response to insulin, which can help regulate menstrual cycles, support ovulation, and reduce symptoms linked to high androgen levels such as acne and unwanted hair growth. Although not FDA-approved specifically for PCOS, metformin is a widely used first-line treatment, especially for women who also have insulin resistance or are struggling to conceive.
What is PCOS and How is Insulin Involved?
Polycystic ovary syndrome (PCOS) is a hormonal disorder affecting about 1 in 10 women of reproductive age. A hallmark of PCOS is insulin resistance: the body’s cells don’t respond as well to insulin, causing the pancreas to produce more. This excess insulin stimulates the ovaries to increase androgen (male hormone) production, worsening symptoms such as irregular periods, infertility, acne, and excess hair.
How Does Metformin Work in PCOS?
Metformin is an insulin-sensitizing medication originally developed for type 2 diabetes. In PCOS, it:
- Decreases the liver’s glucose production
- Enhances glucose uptake by muscles
- Lowers circulating insulin levels
By reducing both insulin and androgen levels, metformin can encourage regular ovulation and menstrual cycles. While its use for PCOS is considered “off-label,” it is recommended by many guidelines due to extensive research and favorable outcomes.
Clinical Benefits of Metformin in PCOS
Metformin offers several clinical benefits for people with PCOS, particularly for those affected by insulin resistance. By addressing underlying metabolic and hormonal imbalances, metformin can help improve symptoms that have a real and lasting impact on daily life. In the following sections, we’ll explore how metformin may regulate menstrual cycles, support ovulation and fertility, reduce androgen-related symptoms like acne and excess hair, and aid in weight management—especially for individuals who struggle with PCOS-related weight gain.
Metformin Regulates Periods
Research shows metformin can help restore predictable menstrual cycles, especially in women whose irregular periods are driven by insulin resistance. By lowering insulin and androgen levels, metformin helps to restore the hormonal balance required for regular ovulation and menstruation. This can lead to more regular periods.
Metformin Supports Ovulation and Fertility
By lowering insulin and androgen levels, metformin increases the likelihood of ovulation. This can be crucial for women trying to conceive and may be used alone or alongside fertility medications such as clomiphene.
Metformin Reduces Androgen Symptoms
High insulin levels can stimulate the ovaries to produce excessive amounts of androgens, often called "male hormones." Lower insulin and androgen levels can gradually improve acne and excessive hair growth, though results may take several months.
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Metformin Helps with Weight Loss
Metformin may support modest weight reduction, particularly in women with insulin resistance. Weight loss not only helps with PCOS symptoms but also reduces the risk of developing type 2 diabetes.
Who Benefits Most from Metformin for PCOS?
Not everyone with PCOS will benefit equally from metformin. This medication is most effective for certain groups of patients—especially those dealing with insulin resistance, metabolic issues, fertility struggles, or weight management concerns. Understanding who is most likely to see improvements with metformin can help guide personalized, effective PCOS treatment plans. Those likely to benefit the most include:
- Women with insulin resistance or features of metabolic syndrome
- Women who are not ovulating but want to become pregnant
- Individuals who are overweight and have difficulty losing weight due to PCOS
Guidelines often recommend metformin for those who have not responded to lifestyle changes or who are facing challenges with fertility.
Side Effects and Risks
Common side effects of metformin include nausea, diarrhea, and stomach upset. These side effects are especially common at the start of therapy, and may improve over time. Lactic acidosis is a more rare but serious side effect that is especially risky for those with liver or kidney problems.
Starting with a low dose and gradually increasing, or using extended-release formulations, can help reduce gastrointestinal side effects. It is also recommended to take each dose before meals.
How Long Does it Take for Metformin to Regulate Periods?
Most women notice improved menstrual regularity within 3–6 months, though this can vary. For fertility, metformin is sometimes combined with other treatments like clomiphene to boost success rates.
Alternatives and Complementary Approaches
Besides metformin, managing PCOS often includes:
- Lifestyle changes: Diet and exercise, which remain the cornerstone for all women with PCOS.
- Hormonal birth control: For those not wishing to become pregnant, these help control periods and androgen symptoms.
- Other medications: Clomiphene and letrozole (for fertility), anti-androgens for severe acne or hirsutism.
- Newer medications: GLP-1 receptor agonists like Ozempic (semaglutide) show promise for PCOS, particularly for weight loss.
This is not all the information you need to know about metformin for safe and effective use and does not take the place of your doctor’s directions. Review the full patient medication guide and discuss this information and any questions you have with your doctor or other health care provider.
References
- American Society for Reproductive Medicine. 2023. International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Accessed on August 4, 2025, from https://www.asrm.org/practice-guidance/practice-committee-documents/recommendations-from-the-2023-international-evidence-based-guideline-for-the-assessment-and-management-of-polycystic-ovary-syndrome/
- Attia, G. M., Almouteri, M. M., & Alnakhli, F. T. (2023). Role of Metformin in Polycystic Ovary Syndrome (PCOS)-Related Infertility. Cureus, 15(8), e44493. https://doi.org/10.7759/cureus.44493
- Carmina, E., & Longo, R. A. (2023). Semaglutide Treatment of Excessive Body Weight in Obese PCOS Patients Unresponsive to Lifestyle Programs. Journal of Clinical Medicine, 12(18), 5921. https://doi.org/10.3390/jcm12185921
- Dumitrescu, R., Mehedintu, C., Briceag, I., Purcărea, V. L., & Hudita, D. (2015). Metformin-clinical pharmacology in PCOs. Journal of medicine and life, 8(2), 187–192. PMCID: PMC4392089 PMID: 25866577
- Eisenhardt, S., et. al. 2006. Early Effects of Metformin in Women with Polycystic Ovary Syndrome: A Prospective Randomized, Double-Blind, Placebo-Controlled Trial, The Journal of Clinical Endocrinology & Metabolism, Volume 91, Issue 3, 1 March 2006, Pages 946–952, https://doi.org/10.1210/jc.2005-1994
- Lashen H. (2010). Role of metformin in the management of polycystic ovary syndrome. Therapeutic advances in endocrinology and metabolism, 1(3), 117–128. https://doi.org/10.1177/2042018810380215
- Melin, J., et. al. 2023. The impact of metformin with or without lifestyle modification versus placebo on polycystic ovary syndrome: a systematic review and meta-analysis of randomized controlled trials. Accessed on August 4, 2025 at https://academic.oup.com/ejendo/article/189/2/S38/7236786
- Palomba, S., et. al. 2009. Evidence-Based and Potential Benefits of Metformin in the Polycystic Ovary Syndrome: A Comprehensive Review, Endocrine Reviews, Volume 30, Issue 1, 1 February 2009, Pages 1–50, https://doi.org/10.1210/er.2008-0030
- Williams, T., Mortada, R., & Porter, S. (2016). Diagnosis and Treatment of Polycystic Ovary Syndrome. American Family Physician, 94(2), 106-113. Accessed on August 4, 2025 at https://www.aafp.org/pubs/afp/issues/2016/0715/p106.html
- Velazquez, E.M., et al. 1994. Metformin therapy in polycystic ovary syndrome reduces hyperinsulinemia, insulin resistance, hyperandrogenemia, and systolic blood pressure, while facilitating normal menses and pregnancy. In: Metabolism - Clinical and Experimental, Volume 43, Issue 5, 647 - 654. Accessed on August 4, 2025 at https://www.metabolismjournal.com/article/0026-0495(94)90209-7/abstract
Read next
Why does metformin cause diarrhea?
Metformin causes diarrhea by changing gut bacteria, affecting bile acid absorption, blocking water absorption in the intestines, and increasing gut-stimulating hormones. These combined effects make stools looser and more frequent.
Continue reading
Can you take metformin without food?
If you take metformin without food you may end up with an upset stomach, especially if you are just starting treatment. Nausea and vomiting is one of the most common side effects with metformin and can occur in over a quarter of patients. Continue reading
Does metformin lower A1C, if so how much?
When metformin is used alone as monotherapy, it lowers A1C by about 1% to 2% on average. A1C is a measure of longer-term blood sugar control. In most patients, metformin is suggested as the initial treatment for type 2 diabetes, but its glucose-lowering effect may not be adequate for all patients if used alone. Continue reading
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Drug information
- Metformin Information for Consumers
- Metformin prescribing info & package insert (for Health Professionals)
- Side Effects of Metformin (detailed)
- Metformin user reviews (660)
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