Metformin for polycystic ovary syndrome (PCOS)

Metformin is used to treat polycystic ovary syndrome (PCOS). Find out how to take it safely and possible side effects.

What is metformin?

Metformin is a tablet commonly used for people with diabetes, but it can also help to reduce some symptoms of polycystic ovary syndrome (PCOS). It helps your body make better use of the insulin it produces and can help with weight loss and blood pressure. Metformin may help to restore your menstrual cycle, as well as helping control excess body hair caused by high testosterone levels. Read more about PCOS and treatment for PCOS.

Metformin has a license in New Zealand for treating type 2 diabetes. However it does not have a license for use in PCOS, so when it is used in this way it as described as ‘off-label’.


In Aotearoa New Zealand metformin is available as tablets (500 mg and 850 mg).

  • The starting dose for adults with PCOS is 500 mg once a day.
  • Your doctor will increase your dose slowly over a few weeks. This allows your body to get used to the medicine and reduces side effects. 
  • The usual dose is 1500–1700 mg per day.

How to take metformin

  • Timing: Always take metformin with food – during a meal or just after a meal. This helps to reduce side effects. Each day's tablets are usually divided into 2 doses (breakfast and dinner), or sometimes into 3 doses (breakfast, lunch and dinner). Try to take your metformin dose at the same times each day, to help you remember to take it.
  • Missed dose: If you forget to take your dose, take it (with food) as soon as you remember. But if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose. 

What to consider when taking metformin for PCOS

Assess whether you need contraception. Be aware that, unlike some other treatments for PCOS, metformin does not act as a contraceptive. Sometimes, people with PCOS who have not got pregnant before taking metformin have got pregnant after starting to take it. If you don't want to get pregnant and you're thinking about taking metformin to control some of the symptoms of PCOS, you should discuss your contraceptive needs and options with an appropriate health professional.

Learn more about what to consider when taking metformin. 

Side effects

The most commonly reported side effects of metformin are tummy upset including nausea (feeling sick), vomiting (being sick) or diarrhoea (runny poos). Side effects are minimised by starting metformin at a low dose and then gradually increase the dose over a few weeks and taking it with a meal. Unlike other medicines used to treat diabetes, metformin does not cause low blood glucose levels (hypoglycaemia or hypos) and therefore it is safe to use. Read more about the side effects of metformin.


  1. Metformin for treating polycystic ovary syndrome in women who are not trying to get pregnant NICE, 2013
Credits: Health Navigator Pharmacists. Reviewed By: Maya Patel, MPharm PGDipClinPharm, Auckland Last reviewed: 22 Mar 2022