A common and under-diagnosed condition
The World Health Organization estimates that polycystic ovary syndrome (PCOS) affects 10–13% of women of reproductive age, and that up to 70% of those affected worldwide have not been diagnosed (WHO fact sheet, 22 January 2026). It is a lifelong condition that affects hormones, metabolism and, for many people, fertility.
How it is diagnosed
There is no single test for PCOS. The WHO describes a diagnosis that requires at least two of three features, once other causes have been ruled out:
- signs of high levels of androgens (hormones such as testosterone), for example excess facial or body hair, hair loss from the scalp, acne or oily skin, or raised testosterone on a blood test;
- irregular or absent periods;
- polycystic ovaries seen on an ultrasound scan.
The name is misleading. The "cysts" are small follicles, not cysts in the usual sense, and the WHO notes that polycystic ovaries on ultrasound are not required for the diagnosis. Someone can have PCOS without polycystic-looking ovaries, and polycystic-looking ovaries without PCOS.
Symptoms
Symptoms vary from person to person and can change over time. The WHO lists irregular, heavy or painful periods, difficulty getting pregnant, excess facial or body hair, thinning hair on the scalp, and acne or oily skin. Many people have only some of these.
Why it matters beyond fertility
PCOS is often discussed only in terms of fertility, but the WHO lists a wider set of associated health risks:
- insulin resistance and type 2 diabetes;
- obesity, high blood pressure and high cholesterol;
- cardiovascular disease;
- diabetes during pregnancy (gestational diabetes);
- sleep apnoea and fatty liver disease;
- endometrial hyperplasia and cancer (thickening of the womb lining, linked to infrequent periods);
- anxiety and depression.
This is why long-term follow-up, such as checks of blood sugar and blood pressure, is part of PCOS care even for people who are not trying to conceive.
PCOS and fertility
PCOS is one of the most common causes of irregular ovulation, which in turn is one of the most common identifiable causes of infertility (see how common is infertility?). Many people with PCOS conceive naturally; others need help to ovulate. The WHO lists medicines that stimulate ovulation, surgery and IVF among the fertility treatments used.
Treatment
There is no cure, but symptoms and risks can be managed. The WHO describes:
- lifestyle changes, including diet and physical activity, which can improve symptoms and metabolic health;
- combined oral contraceptive pills to regulate periods and reduce androgen-related symptoms;
- medicines that block androgens, for excess hair and acne;
- fertility treatments for those trying to conceive.
Treatment is usually tailored to the symptom that matters most to the person at a given time, which may change over the years.
PCOS is not endometriosis
The two conditions are sometimes confused because both can cause period problems and fertility difficulties. Endometriosis involves tissue similar to the womb lining growing outside the womb and typically causes pain; PCOS is a hormonal and metabolic condition. See endometriosis explained.
Tests you may hear about
People with PCOS often have high levels of anti-Müllerian hormone (AMH), because they have many small follicles. AMH tests are sometimes marketed as fertility tests; our article on what an AMH test can and cannot tell you explains their limits.
This article summarises official guidance and is not medical advice. If you have irregular periods or other symptoms described here, talk to a GP.
PCOS at different ages
Irregular periods are common in the first years after periods start, which means that diagnosing PCOS in adolescents is approached with particular care, and doctors may prefer to monitor symptoms over time. In adulthood, PCOS often comes to attention either because of skin and hair symptoms or because of difficulty conceiving. Later in life, the metabolic risks, such as type 2 diabetes and cardiovascular disease, become the main focus of follow-up.
Lifestyle and weight
The WHO lists lifestyle changes first among treatment options. For people with PCOS who are overweight, even modest weight loss can improve periods, ovulation and metabolic health. But PCOS also occurs in people of normal weight, and advice that focuses only on weight can be unhelpful or stigmatising. Regular physical activity and a balanced diet are recommended for their own benefits, whatever a person's weight.
Planning a pregnancy with PCOS
People with PCOS who want to conceive are advised to follow the general preparation guidance, including folic acid, and some may be advised to take a higher dose; a GP can confirm this (see before trying for a baby). Because PCOS increases the risk of diabetes in pregnancy, blood sugar checks are often part of antenatal care.
Common misunderstandings
- "PCOS means you cannot get pregnant." Many people with PCOS conceive naturally; others need help to ovulate, and treatments are often effective.
- "It only affects people who are overweight." PCOS occurs across all body sizes, although weight can influence symptoms and metabolic risks.
- "The cysts need to be removed." The "cysts" are small follicles, not growths that need surgery; ultrasound findings are only one of the possible diagnostic criteria.
- "It goes away after menopause." Periods stop, but the metabolic risks associated with PCOS remain relevant later in life.
For most people with PCOS, the condition is manageable: understanding the diagnosis, treating the symptoms that matter most at each stage of life, and keeping an eye on long-term health usually allow a normal life, including pregnancy for those who want it.