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PCO vs PCOS: Is there a difference?

PCO vs PCOS: Is there a difference?

Despite affecting 1 in 10 women in the UK, PCOS (polycystic ovary syndrome) remains a misunderstood and misdiagnosed condition (1). Confusingly, it’s also often conflated with PCO (polycystic ovaries). But the two are different.
PCOS is a complex metabolic syndrome characterised by insulin resistance and hormone imbalances. PCO, on the other hand, refers to a cluster of cysts on the ovaries. Although some women with PCOS will have PCO, it’s not a given.


PCO is defined as the presence of polycystic ovaries – that is, ovaries with multiple small cysts on the surface, generally more than 12 on each ovary.
Every month, the ovaries release a mature egg from their many follicles. If, however, the follicle doesn’t ‘open’ to release an egg, it can form a small cyst.
Ovarian cysts are very common. In most cases, they don’t cause symptoms and disappear without treatment (3). Many women discover they have PCO during a routine ultrasound for pregnancy or another condition, which picks it up incidentally.
Offers You’ll only become conscious of ovarian cysts if they increase in size, as they may cause bloating, pelvic pain, or menstrual symptoms. If you notice any of these changes, always chat with your GP.


PCOS is less common than PCO but still fairly prevalent among women. It’s estimated that around 75 per cent of women living with PCOS are yet to be diagnosed (2).
Though the cause of PCOS is unknown, most experts agree PCOS is driven by insulin resistance and hormone imbalances, specifically high levels of androgens – sometimes referred to as ‘male’ hormones.
The physiological changes associated with PCOS can lead to a range of challenging symptoms. These include weight gain, excessive hair growth (hirsutism), and acne, as well as menstrual irregularities, which are often behind fertility issues. 
Owing to the distressing nature of symptoms – and the hormone imbalances themselves – many women with PCOS also experience mental health challenges, like increased anxiety, depression, and low self-esteem.
If you have symptoms of PCOS, they will usually appear during your teens or early 20s.
You can learn more about PCOS here.


Polycystic ovaries are a component of polycystic ovary syndrome. But PCO alone doesn’t indicate PCOS.
To diagnose PCOS, you need two out of three criteria present; polycystic ovaries are just one of these. The other two are irregular periods and higher-than-normal androgen levels (4).
All this is to say the name 'polycystic ovary syndrome' is a little misleading. You don’t need cysts on your ovaries to receive a diagnosis. Some scientists and healthcare providers believe the term 'PCOS' is such a misnomer that they're campaigning to change it to avoid confusion.
Another key difference is PCOS is a ‘syndrome’, earmarked by various associated symptoms. PCO, on the other hand, is more of an isolated event.

Find out more about PCOS

PCO and PCOS may sound similar, but they’re different health-related events. PCO refers to multiple cysts on the ovaries, while PCOS is a multi-layered endocrine condition characterised by insulin resistance and excessive androgen levels.
Though PCO can be symptomatic of PCOS, it’s not the only indication. Many women have PCOS without PCO. 
If you found this look into polycystic ovaries and polycystic ovaries syndrome useful, you can find similar guidance on our dedicated health hub. Alternatively, please get in touch with our team of expert Nutrition Advisors, who are on hand to provide free, confidential advice. 



  1. (2023) NHS choices. Available at:

  2. Yasmin E, Balen AH. (2007) The diagnosis of polycystic ovary syndrome: the criteria are insufficiently robust for clinical research. Clin Endocrinol (Oxf). 67(6): 811-815.

  3. Ovarian cyst (2023) NHS inform. Available at:

  4. Diagnosis. Polycystic ovary syndrome (2023) NHS choices. Available at:

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Disclaimer: The information presented by Nature's Best is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications.

Our Author - Olivia Salter


Olivia Salter has always been an avid health nut. After graduating from the University of Bristol, she began working for a nutritional consultancy where she discovered her passion for all things wellness-related. There, she executed much of the company’s content marketing strategy and found her niche in health writing, publishing articles in Women’s Health, Mind Body Green, Thrive and Psychologies.

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