Is vitamin B12 good for PCOS?

You may have read about the recent link between PCOS and vitamin B12, in particular for people with PCOS taking metformin. We’re going to cover what PCOS and vitamin B12 are, and the link between the two.

What is PCOS?

Polycystic ovary syndrome (PCOS) is a condition affecting how one’s ovaries work. Whilst there are multiple symptoms including; irregular periods, difficulty getting pregnant, excessive hair growth, changes in weight, thinning hair on the head and acne. The 3 main diagnostic criteria are as follows:

• Irregular periods

• Excess androgen (male hormones)

• Polycystic ovaries

For a diagnosis your healthcare professional will assess the above, and provide a diagnosis if you meet 2 out of the 3 criteria.

What is Vitamin B12?

Vitamin B12 is a water-soluble vitamin, which is fundamental for the metabolism of fatty acids and amino acids, for normal blood formation and neurological function. It is most commonly found in meat, fish and dairy and not reliably in plant foods. B12 deficiency can occur if high enough sources are not consumed, for example on a vegan diet, signs of early deficiency include fatigue and anaemia. It is therefore recommended to take vitamin B12 supplements if you are at risk of deficiency.

Vitamin B12 and PCOS

A commonly recommended medication for individuals with PCOS is the insulin-sensitizer metformin. However, research has shown that long-term use of metformin at high doses can deplete levels of vitamin B12.

One of the largest studies investigating the link between metformin and vitamin B12 was through the diabetes prevention programme, concluding long term use of metformin was associated with B12 deficiency and anaemia.

Unfortunately, studies specifically looking at metformin use in individuals with PCOS are less common. However, a systematic review and meta-analysis looking at individuals with PCOS and individuals with type 2 diabetes found the higher the dose of metformin the more deficient individuals were in vitamin B12.

Vitamin B12 Deficiency Taking Metformin

Individuals with PCOS may be at an increased risk of vitamin B12 deficiency if they are taking metformin. If you think you may be at risk of vitamin B12 deficiency and are experiencing any of the below symptoms it is important to consult with your healthcare professional:

• Extreme tiredness

• Pins and needles (tingling in your hands or feet)

• Problems with memory, understanding and judgement

• Feeling weak

• Disturbed vision

Whilst it is important to diagnose and treat B12 deficiency as soon as possible, most cases can be easily treated with injections or tablets to replace the missing vitamins.


  1. NHS, 2019

  2. NHS, 2019

  3. Aroda et al., 2016

  4. Liu et al., 2014

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