Polycystic ovarian syndrome (PCOS) is a medical condition that affects between 8% and 13% of reproductive-aged women.

Women with PCOS are not able to ovulate, or release eggs, properly. Ovaries become enlarged and contain fluid-filled sacs (follicles) surrounding the eggs. If you have PCOS, you may have irregular periods and excess facial or body hair.

Metformin is sometimes used to manage the symptoms of PCOS. While it’s only licensed to treat type 2 diabetes, it can be used “off-label” for PCOS in certain circumstances.

So, how does it work? And is it safe to take Metformin for PCOS?

How Does Metformin Treat PCOS?

Metformin lowers the insulin and blood sugar levels of women with PCOS. According to the NHS, it can stimulate ovulation, encourage regular monthly periods and lower the risk of miscarriage.

Many women with PCOS (but not all) have something called ‘insulin resistance’. This is when the cells in their body don’t respond well to insulin, which controls blood sugar levels. This can cause levels of insulin in their body that are higher than normal. 

Metformin increases sensitivity to insulin, so the body is better able to control blood sugar levels and lower insulin overproduction.

How Do You Take Metformin?

Metformin comes in small tablets you take either once or twice throughout the day.

You can get immediate-release tablets or extended-release tablets. The type of tablet determines how large the dose is and how often you need to take them. 

Your doctor will tell you what dosage is right for you. For people who are pre-diabetic, the starting dose is usually lower than someone who has type 2 diabetes.

Is Metformin Safe? Potential Side Effects

Common metformin side effects include:

  • Nausea and vomiting 
  • Diarrhoea
  • Stomach pain
  • A metallic taste in the mouth or changes to taste

Stomach side effects, like nausea, are more common when you start treatment. To reduce these side effects, most people are given a low dose to begin with, which will gradually increase.

Although rare, serious side effects include lactic acidosis and allergic reactions. 

For more information on Metformin side effects, see the patient information leaflet or call your doctor or pharmacist. You should also let them know if you do have side effects.

Who Is Metformin Suitable For?

Not everyone with PCOS will be able to take Metformin. 

Some people’s PCOS may not be severe enough to need this medication, as it is potent. They may be able to use alternative medication that isn’t quite as powerful and that doesn’t cause as severe side effects.

Speak to your doctor to find out if Metformin is right for you.

Summary

  • Although Metformin is only licensed for type 2 diabetes, it can be used “off-label” to help manage PCOS symptoms.
  • Metformin lowers insulin and blood sugar levels in women with PCOS. It can stimulate ovulation, regulate periods, and reduce the risk of miscarriage.
  • Metformin is available in immediate-release or extended-release tablet forms. The dosage and frequency of intake are determined by a doctor, typically starting with a lower dose to minimise side effects.
  • Common side effects of Metformin include nausea, diarrhoea, and stomach pain. It may not be suitable for everyone with PCOS, especially those with less severe cases. Alternative treatments may offer fewer side effects.

References

World Health Organization (2023). Polycystic ovary syndrome. [online] World Health Organization. Available at: https://www.who.int/news-room/fact-sheets/detail/polycystic-ovary-syndrome.

NHS (2022). Treatment – Polycystic ovary syndrome. [online] NHS. Available at: https://www.nhs.uk/conditions/polycystic-ovary-syndrome-pcos/treatment/.

Editor’s note: This article was originally published on March 2, 2018. It has been updated for accuracy, readability and comprehensiveness.