Pros and Cons of Metformin for PCOS

Often we come across individuals prescribed metformin without understanding why they have been prescribed this medication that they associate with type 2 diabetes. It is important to take the time to understand metformin and how it works for PCOS in order to weigh the pros and cons as to whether it is the right choice for you. 

What is PCOS?

Polycystic Ovarian Syndrome or PCOS is a common endocrine or hormone disorder. Many individuals that have PCOS will look very different from diverse body shapes and sizes alongside symptoms presenting.  There is no ‘typical’ person with PCOS, as it is so variable. Often the symptoms include menstrual cycle disturbances, acne, and unwanted hair growth, commonly on the face. If you have an ultrasound scan you may find a ‘pearl-like’ structure around the outside of the ovary known as cysts. 

What is metformin?

Metformin is characterised as a biguanide drug and an oral antihyperglycemic agent (OHA). It is a prescribed medication to manage insulin resistance as it helps your body utilise the insulin your body is making better and also reduces the amount of blood glucose created by different mechanisms such as gluconeogenesis in the liver. Therefore metformin has a licence in the UK for treating individuals with type 2 diabetes. However it does not have a licence for use in PCOS, so use in this way is described as ‘off-label’ and usually, it will be initiated by a specialist doctor.

What is insulin resistance?

One symptom and driver of PCOS is insulin resistance. Up to 95% of people with PCOS have insulin resistance, no matter their body weight or shape. Insulin resistance is the term used to describe your body unable to utilise insulin (a hormone) properly to allow your cells to use glucose (sugar molecules) from the blood. Consequently, your body tries to overcome this by producing more insulin than it should. This means your pancreas, the organ secreting insulin, is working harder which is why if a person with type 2 diabetes is not optimally managed for several years this can result in insulin injections being the main treatment. 

What are the pros of taking metformin for PCOS?

As mentioned metformin is a first-line pharmacological treatment for individuals diagnosed with type 2 diabetes mellitus because of its positive profile, including its insulin-sensitising agent, weight-neutral effects, and low risk of hypoglycemia. It has also been shown to have cardioprotective benefits. 

Subsequently it can be prescribed ‘off-label’ for treating insulin sensitivity in individuals with PCOS, which as it states aims to improve your fasting blood glucose levels. Random clinical studies have also demonstrated the benefits of metformin on reducing other symptoms of PCOS including hirsutism, ovulation, infertility and further into pregnancy by minimising the risk of miscarriages in the first 12 weeks and gestational diabetes for those with PCOS. This was recently supported in March 2022 by European studies that found no safety concerns with metformin in pregnancy. 

Lastly, if you have a history of functional gastrointestinal symptoms such as being diagnosed with irritable bowel syndrome then you can also discuss with your doctor about the metformin modified-release medication as an option which is usually better tolerated.

What are the cons of taking metformin for PCOS? 

The most common side effects from taking metformin are problems affecting the stomach and bowel, such as nausea and vomiting, diarrhoea, abdominal pain and loss of appetite. These side effects occur in more than 1 in 10 people taking metformin but they most often happen at the beginning of treatment. The National Institute of Clinical Excellence (NICE) guidance regarding metformin for individuals with PCOS, they provide a list of questions you can discuss with your prescribing Doctor. 

Most recently in June 2022, studies found that a common side-effect of a high dose and long-term prescription of metformin is vitamin B12 deficiency therefore blood tests should be used to monitor levels of vitamin B12. If required guidance on how to supplement should be sought or if needed to stop metformin medication altogether under the guidance of your doctor. 

What is the dosage of metformin for PCOS?

In the UK the dosage of metformin for PCOS usually begins between 250mg to 500mg per day and gradually builds up to 2g of metformin per day depending on side effects experienced. The gradual increase of metformin taken daily usually occurs weekly until the goal dose is achieved and can vary from person to person.

4 ways you can help reduce side effects when taking metformin

  1. As directed by your doctor or specialist is to take with meals to make sure you are not taking metformin on an empty stomach. For example breakfast, lunch or evening meal
  2. Ensure the meal you have is substantial, for example containing a source of carbohydrate, protein and vegetables to create an overall balance.
  3. Be absolutely clear as to the amount of metformin you are taking daily and when, if any higher amounts are due to begin with your Doctor 
  4. If you have a history of gastrointestinal discomfort discuss the possibilities of trialling the metformin modified-release medication instead

Is there any natural alternative to metformin?

There is limited evidence comparing the efficacy of metformin to natural alternatives. However, one natural alternative that has a significant evidence base which you may have heard about before is inositol. 

Inositol is a type of sugar alcohol needed by almost every tissue in the body which acts as a vitamin-like substance involved in many cellular pathways. One of the key pathways is as a messenger involved in insulin signalling. You can find inositol naturally in common foods such as nuts, beans and wholegrains. There has been growing evidence supporting the supplementation of inositol in improving insulin resistance and sex hormone ratios for people with PCOS, that in turn provides a positive effect on fertility and ovulation.

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