What to Know About Taking Metformin for PCOS

If you have PCOS and have been prescribed metformin, chances are you have a lot of questions and concerns about taking this medication. The majority of people with PCOS have high insulin levels which causes weight gain, cravings, and even dark patches on your skin. Over time, exposure to high insulin levels can make you insulin resistant or turn into type 2 diabetes. Metformin is a well-known medication used for PCOS, which works to lower your insulin and reduce your risk for diabetes.

This article will tell you what you need to know about taking metformin if you have PCOS, how to manage side effects, as well as alternative treatments.

How Does Metformin Work?

Metformin is one of the oldest the most studied drugs available in the United States. It’s been around over 30 years, more than most drugs on the market. Other names for metformin include glucophage, glucophage XR, glumetza, and fortamet. Although it’s not labeled for use in individuals with PCOS, metformin is one of the most common medications used to manage the condition.

Metformin works as an insulin-sensitizer to reduce your production of glucose. Metformin lowers blood glucose and insulin levels in three ways:

  1. It suppresses the liver’s production of glucose.
  2. It increases the sensitivity of your liver, muscle, fat, and cells to the insulin your body makes.
  3. It decreases the absorption of carbohydrates you consume.

The average dose of metformin for people with PCOS is 1,500 mg to 2,000 mg daily.

Health Benefits of Metformin

Besides lowering your glucose and insulin levels, metformin may provide other health benefits to people with PCOS. Metformin can improve fertility by enhancing ovulation and regulating menstrual cycles. This means if you are sexually active, you should use birth control to prevent pregnancy, even if you haven’t been getting your period regularly. Metformin may even improve cholesterol levels and hirsutism symptoms like acne and excess hair growth.

Taking metformin while pregnant may reduce the risk of gestational diabetes and should be discussed with your physician.

Metformin has been studied in girls as young as 8 years of age, with some researchers recommending it to prevent the onset of PCOS.

Emerging research has showed that metformin may be used to prevent and treat cancer. Read more about it in our article CAN METFORMIN TREAT AND PREVENT CANCER?

What about the Side Effects of Metformin?

Overall, most people with PCOS can tolerate metformin just fine. You tend to hear about the worse cases online because they are the ones having problems. The most common side effects experienced when you first start taking metformin for PCOS are GI related and may include nausea, gas, bloating, abdominal discomfort and diarrhea. Some people find that the extended-release version of metformin is gentler on the digestive system and better tolerated, however, some have questioned whether the extended-release version is as effective.

Metformin should be taken with food to minimize side effects. Slowly increasing the dose of metformin over several weeks is recommended for best results. Eating sugary and processed foods can worsen the digestive side effects of metformin. You may find working with a registered dietitian nutritionist helpful to create a meal plan that works best for your unique needs.

Metformin can affect the absorption of vitamin B12. Long-term use and high doses of metformin increase the likelihood of a vitamin B12 deficiency.  A lack of vitamin B12 can cause mood changes, memory loss and can cause permanent damage to the brain and nervous system. You should supplement your diet with vitamin B12 and have your levels checked annually. Optimal ranges of vitamin B12 should be >450 pg/mL. Elevated serum homocysteine and urinary methylmalonic acid (MMA) levels, the gold standard in assessing B12, also indicate a B12 deficiency.


PCOS Multi

PCOS MULTI® has been specifically formulated to include higher levels of vitamin B12 and other vitamins and minerals that people with PCOS tend to be deficient in.

Lactic acidosis is a rare side effect of metformin. When you metabolize metformin, lactic acid is produced and can in rare cases, build up to toxic levels. If you take metformin limit alcohol intake to no more than one drink a day for women and 2 drinks a day for men.

A review of 10 studies showed prenatal exposure to metformin is associated with an increased weight in children, but not with height or BMI. More research is being done in this area.

the pcos workbook: your guide to complete physical and emotional health

Are There Natural Alternatives to Metformin?

There isn’t an exact substitute for metformin but for those individuals who can’t tolerate it or don’t want to take a prescribed medication, or want to try adding in something else, there are other ways to improve insulin sensitivity if you have PCOS-and without the harsh GI side effects.

Of course, the most important thing is having balanced meals and engaging in regular physical activity. Getting good sleep and managing stress are also key. No pill can replace a healthy lifestyle.

N-acetyl cysteine (NAC)

N-acetyl cysteine (known as NAC), is an antioxidant that has been shown to work as well as metformin for reducing insulin and cholesterol levels in women with PCOS. The recommended dosage of NAC is 900 mg to 3 grams daily. Bonus: NAC can also improve egg quality in those with PCOS and is great to use to keep the immune system healthy.


Inositol is well studied in PCOS and has been shown to lower insulin levels right at the cell level, targeting an area that metformin does not. In this video, I talk about how inositol works to “fix the defective doorbell seen in PCOS.” A combined amount of Myo insositol to d-chiro inositol in the ideal 40:1 ratio has also been shown to be better at improving insulin and other metabolic aspects of PCOS than either inositol alone. The combined ratio is the ratio in our bodies. Ovasitol has this unique ratio.

For more info on inositol, see our posts:





Berbrine is a Chinese herb that has been used for thousands of years as a treatment for diabetes and infertility. As a potent insulin sensitizer, berberine’s insulin and glucose lowering effects have been compared with that of metformin, although the two work differently. Berberine improves insulin signal transduction by stimulating glucose intake via the activation of the AMP-activated protein kinase pathway.

After 3 months of use, women who took berberine (500 mg, 3x daily), saw similar reductions in glucose and insulin levels than metformin (500 mg, 3x daily), or placebo.

Women with PCOS who took berberine also saw significant reductions in total cholesterol, LDL (bad cholesterol levels), and triglycerides and a significant improvement in HDL (good cholesterol levels), more than metformin.

Interested in learning more about berberine? Check out 10 Big Benefits of Berberine for PCOS


Magnesium is an important mineral that women with PCOS have been shown to be significantly lacking in. Magnesium has been shown to play a role in glucose and insulin regulation.

Magnesium is important to help glucose enter cells where it is used for energy. Part of its job in doing this is regulating the function and transport of insulin, which acts as a key to open the cell doors to glucose. Without enough magnesium, glucose doesn’t enter the cells in sufficient amounts. This can cause fatigue and difficulties regulating blood sugar. Sufficient levels of magnesium can therefore improve insulin resistance and reduce your risk for developing type 2 diabetes.


All of the above supplements can be taken together and in conjunction with taking metformin. For many, adding these supplements while taking metformin can be effective for helping to lower insulin and cholesterol levels or improve fertility. Keep in mind, everyone is different and responds to both metformin and these supplements differently.

Share with us your experience taking metformin. Did it help you or not?

angela grassi PCOS dietiitian nutritionistAngela Grassi, MS, RDN, LDN, is the founder of The PCOS Nutrition Center, for which she has been providing evidence-based nutrition information and coaching to people with PCOS for over 20 years. Angela is the author of several books on PCOS, including PCOS: The Dietitian’s Guide, The PCOS Workbook: Your Guide to Complete Physical and Emotional Health, and The PCOS Nutrition Center Cookbook. Angela is the past recipient of The Outstanding Nutrition Entrepreneur Award, The Award in Excellence in Practice in Women’s Health, and The Award for Excellence in Graduate Research, from the Academy of Nutrition and Dietetics. Having PCOS herself, Angela has been dedicated to advocacy, education, and research of the syndrome. Click here to schedule a session with Angela to learn more about how nutrition coaching for PCOS can help you!


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  2. Zhuo Z, Wang A, Yu H. Effect of metformin intervention during pregnancy on the gestational diabetes mellitus in women with polycystic ovary syndrome: a systematic review and meta-analysis. J Diabetes Res. 2014;2014:381231.
    Oner G, Muderris II. Clinical, endocrine and metabolic effects of metformin vs N-acetyl-cysteine in women with polycystic ovary syndrome. Eur J Obstet Gynecol Reprod Biol. 2011.
    Costantino D, Minozzi G, Minozzi E, Guaraldi C. Metabolic and hormonal effects of myo-inositol in women with polycystic ovary syndrome: a doubleblind trial. Europ review med pharmacol sci. 2009;13(2):105-110.
  3. Le Donne M, Alibrandi A, Giarrusso R, Lo Monaco I, Muraca U. [Diet, metformin and inositol in overweight and obese women with polycystic ovary syndrome: effects on body composition]. Minerva ginecologica. 2012;64(1):23-29.
  4. Januszewski M, et al. Metabolic and hormonal effects of a combined Myo-inositol and d-chiro-inositol therapy on patients with polycystic ovary syndrome (PCOS). Ginekol Pol. 2019;90(1):7-10.
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Comments (5)
  • Megan

    December 12, 2019 at 9:55 am

    Metformin was extremely helpful for me. It helped me to lose weight that I had been trying to lose for a year. It also took away my sugar cravings!!!! After being on it for 3 months I was able to become pregnant and continued taking it into my second trimester with no adverse side affects. I did notice that if I ate anything heavy in sugar it ran through me, so I had to be mindful of what I was eating.

  • Angela Grassi

    December 12, 2019 at 10:11 am

    That’s great to hear. Glad Metformin has helped you!

  • Mary Ogletree

    February 20, 2021 at 10:29 am

    I have pcos I have had PCOS 15yrs on metformin prescription 500mg to manage my PCOS and I also take vitamins.im 53years old.

  • Krista

    March 24, 2022 at 10:46 am

    Thank you for this very helpful article! Do you recommend taking metformin and myoinositol together? Or is it better to pick one and simply stick with that?

  • Angela Grassi

    April 4, 2022 at 10:18 am

    Everyone is different. You can take both together safely. Here’s my review of taking both together: https://www.pcosnutrition.com/ovasitol-review-pcos/

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