If you have unpredictable periods, persistent acne or new facial hair, you may wonder whether polycystic ovary syndrome (PCOS) explains the pattern. In the UK, a PCOS diagnosis is not based on one blood result or scan. Your GP looks at your symptoms, considers other possible causes and decides which investigations are useful. The NHS now uses the newer name polyendocrine metabolic ovarian syndrome (PMOS), but many people and clinics still know it as PCOS.
Where the UK diagnosis process starts
Book a GP appointment if your periods are unusually far apart, you have troublesome acne or excess hair growth, or you are finding it difficult to conceive. A clinician will usually ask when your periods began, how often they arrive, whether symptoms have changed and which medicines or contraceptives you use.
They may also ask about weight changes, family history, hair thinning, sleep and emotional wellbeing. Blood pressure and other health checks may be offered.
PCOS diagnostic criteria: what actually counts?
For adults, clinicians generally use a modified version of the Rotterdam criteria. After excluding other explanations, at least two of three features are needed:
First, irregular or absent ovulation, often suggested by infrequent or absent periods. Second, signs of increased androgen activity, such as coarse facial hair, or elevated androgen levels on blood tests. Third, an appearance of polycystic ovaries on an appropriate scan; in adults, specialist guidance also allows anti-Müllerian hormone (AMH) to be used as an alternative way to assess this feature in suitable circumstances.
This means a person with infrequent periods and clear evidence of androgen excess may meet the criteria without an ultrasound. Equally, an ultrasound showing many follicles is not enough on its own to diagnose PCOS. Despite the condition’s traditional name, these follicles are not the same as dangerous ovarian cysts.
For example, someone aged 27 who has periods every two or three months and increasingly coarse chin hair could be assessed for PCOS even if a previous scan looked normal. The GP must still consider alternative causes before confirming the diagnosis.
Which PCOS blood tests might you have?
There is no single positive-or-negative PCOS blood test. The selection depends on your symptoms, age and medical history. Common investigations include:
Testosterone, sometimes alongside sex hormone-binding globulin and a calculated free androgen index, to assess androgen activity. Thyroid function and prolactin tests may help rule out other causes of disrupted periods. Depending on the findings, a clinician may request further hormone tests, including investigations for less common adrenal conditions.
Tests for glucose regulation and cholesterol assess associated health risks rather than prove the diagnosis. The clinician may recommend HbA1c or a glucose tolerance test, depending on individual risk and current guidance. An elevated luteinising hormone-to-follicle-stimulating hormone ratio is not required for a PCOS diagnosis.
Combined hormonal contraception can change androgen measurements and menstrual patterns. Tell your GP if you use the pill, patch or vaginal ring. Do not stop contraception simply to prepare for PCOS tests; if specialist testing requires a break, your clinician should discuss timing and reliable alternative contraception with you.
When is a PCOS ultrasound useful?
A PCOS ultrasound can help if the diagnosis remains uncertain after your history and hormone assessment. An abdominal scan uses a probe over the tummy; a transvaginal scan may give more detailed images in adults when it is appropriate and you consent. You can discuss which approach feels acceptable.
Scans assess ovarian size and the pattern of small follicles. Modern diagnostic guidance uses updated follicle thresholds, so an older report may not translate neatly into today’s criteria. If irregular cycles and androgen excess are already established, a scan is often unnecessary solely to confirm PCOS.
AMH testing is an option for assessing ovarian morphology in adults under the 2023 international guideline, but it is not a stand-alone diagnostic test and is not automatically offered in every NHS pathway. A clinician would generally choose either AMH or ultrasound for this purpose, not both routinely.
Why diagnosis differs for teenagers
Periods can be irregular in the years after they first begin, and ultrasound appearances can overlap with normal adolescent development. For teenagers, diagnostic guidance requires both persistent ovulatory problems and evidence of androgen excess, after other causes are excluded. Ultrasound and AMH are not recommended for diagnosing PCOS in adolescents.
A young person with possible signs may be described as being at increased risk and offered follow-up rather than an immediate label.
What happens after the results?
Your GP should explain which criteria you meet, which conditions have been excluded and whether any further assessment is needed. If the results are inconclusive, ask what would justify repeating a test or arranging a review. Sudden, rapidly worsening facial hair or voice deepening needs prompt medical assessment because it is less typical of PCOS.
After a diagnosis, treatment should reflect what matters to you. Options may include help with irregular bleeding, acne or unwanted hair; support for ovulation if pregnancy is a goal; and assessment of blood pressure, glucose and cholesterol. Long gaps without periods deserve attention because protecting the womb lining can be important. A gynaecologist or endocrinologist may become involved for complex symptoms or fertility concerns.
You do not need to have excess weight to have PCOS, and lifestyle advice should be tailored rather than presented as a cure. Our related guides to irregular periods, hormonal acne and insulin resistance can help you prepare more focused questions for your next appointment.
How to prepare for your appointment
Bring a record of recent period dates, including missed cycles, and note when acne, hair changes or other symptoms began. List medicines, supplements and contraception, and mention any previous scans or hormone results. A useful question is: “Which two diagnostic features do I meet, and what other causes have you ruled out?” This can turn a confusing series of tests into a clearer plan.
Frequently asked questions
Can I be diagnosed with PCOS if my ultrasound is normal?
Yes. In an adult, irregular ovulation and evidence of androgen excess can be enough once other causes have been excluded. The scan does not have to show polycystic ovaries.
Can normal testosterone levels rule out PCOS?
No. Some people have clinical signs of androgen excess despite results within the laboratory range. Your clinician considers the complete history, examination and the reliability of tests.
How long does a PCOS diagnosis take on the NHS?
There is no fixed timetable. It depends on GP appointments, laboratory testing, whether imaging is needed and local referral waiting times.
Do I need to see a specialist?
Not always. A GP can often assess and manage straightforward cases, while a gynaecologist or endocrinologist may help if the diagnosis is uncertain, symptoms are severe or fertility treatment is needed.
The next sensible step
PCOS diagnosis in the UK is a process of putting symptoms and carefully selected tests together, not collecting every possible investigation. If you suspect PCOS, take a period history to your GP and ask how the criteria apply to you.