On metformin for PCOS

Have you been put on metformin for PCOS? Metformin is a medication known for its use in the treatment of diabetes mellitus type, but a good number of women are being put on metformin for PCOS. In this article, we are going to be discussing about why your doctor may have put you on insulin for PCOS, what evidence and research show for using metformin for PCOS , how metformin may help people who suffer from PCOS, side effects of metformin  and how to take your metformin.

Insulin resistance and PCOS

Many, but not all women who have PCOS also have ‘insulin resistance’. Insulin resistance can lead to higher than normal insulin levels. This high level of insulin can cause thickening and darkening of the skin on the back of the neck, the groin area and under the armpit. This is known as acanthosis nigricans. These high levels of insulin can also disturb the normal balance of the male and female hormones and make the ovaries to produce more male hormone e.g. testosterone. This leads to some of the symptoms like hirsutism (excessive body hair), acne, irregular or few period or problems getting pregnant which are experienced by women who have PCOS.

Having a higher insulin level can make you to gain weight. This may explain why many women with PCOS are overweight or obese. These elevated insulin levels can also increase your chances of developing type 2 diabetes and endometrial cancer (cancer in the lining of the womb).

On Metformin for PCOS

Metformin is the only biguanide available and is commonly used as a first-line treatment for people with type 2 diabetes.

 It is available in different forms – tablets for immediate release which can be taken up to three times per day or prolonged release which is usually taken once a day and oral solution and powder for oral solution for immediate release. If prescribed the prolonged release metformin, you must swallow whole. Do not chew, break or crush. If prescribed other forms like the immediate release form, you can chew, break and crush before taking it.

Many, but not all women who have PCOS also have ‘insulin resistance’. Metformin can also lower insulin and blood sugar levels in women who have PCOS. Women who have high insulin levels and take Metformin are less likely to develop type 2 diabetes than those who don’t take a metformin or other insulin lowering medication.

On metformin for PCOS

Research have demonstrated that overweight women with PCOS and treated with Metformin while maintaining a healthy lifestyle by healthy eating and exercise were able to lose weight and reduce their fasting blood sugar levels. The studies also showed that taking Metformin while maintaining a healthy weight improved cholesterol levels.

How does metformin work?

Biguanides reduce blood sugar levels by stopping the liver from producing new glucose as it prevents the liver from converting fats and amino acids into glucose. It also helps to overcome insulin resistance and improve the body’s sensitivity towards insulin by activating an enzyme (AMPK). This enzyme helps cells to respond more effectively to insulin and take in glucose from the blood.

Side effects of metformin

The most common side effects of metformin are gastrointestinal disturbances like nausea and vomiting, abdominal pain, flatulence and loss of appetite especially if taken at high doses. Most women are able to tolerate it very well, especially if they start taking a small dose and increase it gradually. Taking metformin with meals can also reduce side effects. Most side effects start at the beginning of treatment and should resolve after about 2 weeks.

Using Metformin together with general anaesthesia can cause ketoacidosis. It is best to suspend metformin on the morning of surgery and restart when renal function returns to baseline (your normal levels). Using Metformin together with iodinated contrast agents can cause renal failure and precipitate lactic acidosis, it is best to suspend metformin before the x-ray and restart after 48 hours if renal function returns to baseline.

Why would you be put on Metformin for PCOS

Several studies have looked at the use of Metformin in women with PCOS and the majority have shown that Metformin can make periods more regular and restore normal ovulation cycles, improve fertility, decrease the rate of spontaneous abortions (miscarriage), help with weight loss, reduces hyperandrogenism, improve insulin resistance and decrease risk of type 2 diabetes in women with PCOS. It can also help reduce hirsutism (unwanted hair growth) even though this may take several months and may not be as effective as other treatments used for hirsutism. Metformin also lowers high cholesterol levels and reduce the risk of heart disease.

Is metformin licenced for PCOS?

Metformin is not licenced in the UK and US for the treatment of PCOS, but because a lot of women with PCOS also has insulin resistance and the effects metformin has been shown to have on how the body responds to insulin suggest it might be helpful in managing the symptoms of PCOS and encourage fertility hence it’s prescribed for PCOS, especially in those who have with impaired glucose tolerance (IGT). Using it this way is called ‘off-label’ use.

What are people on metformin for PCOS saying?

Remember that providing you with a link to where to read reviews does not mean an intention to endorse or recommend any medication or therapy. The reviews should not be used to substitute the expertise, knowledge, judgement and skills of the healthcare professional.

According to the review by Drugs.com (https://www.drugs.com/comments/metformin/for-polycystic-ovary-syndrome.html) of people taking metformin for PCOS,

What dose on metformin for PCOS?

To start metformin for PCOS Royal Berkshire hospital suggest two routes depending on if you are getting side effects or not.

Quick route:

500mg a day for 1 – 2 weeks then

500mg twice a day for 1 – 2 weeks then

500mg three times a day or 850mg twice a day for 1 – 2 weeks then

1g twice a day or 850mg three times a day thereafter

It is advised that the dose of metformin is not increased when you have side effects; instead that you wait until these side effects have settled.

Slow route (in women with side effects):

Week 1 250mg once a day

Week 2 250mg twice a day

Week 3 250mg three times a day

Week 4 500mg twice a day

Week 5 500mg three times a day

Week 6 1g twice a day

While it there is no specific time limit to be on metformin for PCOS, if you have taken it for six months and have not had any beneficial effect then your doctor could consider discontinuing it.

Metformin for fertility

A recent Cochrane review suggests that metformin may be beneficial over placebo for live birth, It also suggests metformin probably increases pregnancy rates and ovulation rates though more women had gastrointestinal side effects.

Some women who did not get pregnant before being put on metformin for PCOS got pregnant after they started taking it. Metformin is not a contraceptive and as it can stimulate fertility, it is important that you discuss contraceptive needs with your doctor if your doctor is considering placing you on metformin for PCOS and you are not trying to get pregnant.

Metformin for Pregnancy complications

Women with polycystic ovary syndrome (PCOS) are at increased risk of having pregnancy complications such as preeclampsia, preterm delivery, late miscarriage and gestational diabetes.

 A recent study from Department of Clinical and Molecular Medicine at the Norwegian University of Science and Technology tested the effectiveness of metformin on PCOS and pregnancy complications showed that metformin may decrease the risk of late miscarriage and preterm birth. Gestational diabetes remained unchanged which suggests that metformin treatment may not have an impact on the risk of developing diabetes during pregnancy. Preeclampsia risk was also found to be unchanged with metformin treatment.

Some important things to note if put on Metformin for PCOS

Make sure your doctor or healthcare professional knows about all the prescribed and over the counter medication that you are taking.

Let your doctor dentist or healthcare professional know you are on metformin for PCOS when booked in for any surgery and they will let you know how long before the surgery that you should not take metformin.

One side effects of metformin are that it interferes and lowers your body’s ability to absorb vitamins B12 and folate. Check with your doctor or healthcare professional if it’s a good idea to take a multivitamin containing B vitamins.

Drinking alcohol while taking metformin can be dangerous as you are more likely to get dehydrated or develop liver problems. Your doctor may not put you on metformin for PCOS if you drink a lot because metformin would not be a good treatment option for you. Your health care professional may either put you on another treatment or ask you to reduce your alcohol intake.

Ensure you use suitable contraceptive if you’re sexually active and don’t want to get pregnant.as metformin can stimulate fertility.


Rotterdam ESHRE/ASRM-Sponsored PCOS Consensus Workshop Group, authors. Revised 2003 consensus on diagnostic criteria and long-term health risks related to polycystic ovary syndrome. Fertil Steril. 2004;81:19-25.

Royal Berkshire NHS Foundation Trust (Accessed 24/6/15). Use of metformin in PCOS.

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Nwasom is a pharmacy graduate and a pharmacist currently practicing in the United Kingdom. I have  great experience communicating with patient and their family as gained through working as a pharmacist in both the hospital and community pharmacy sector. I love writing so it was a natural thing to try and pass medical and health information on through writing.