The Rotterdam Criteria: How PCOS Is Officially Diagnosed
If you have read anything about PCOS diagnosis, you have probably come across the "Rotterdam criteria." It sounds technical, but the idea behind it is straightforward, and understanding it can demystify how doctors actually reach a PCOS diagnosis. Zoey connects you with MOH-licensed Singapore doctors who can carry out an assessment and explain what the criteria mean for you.
There is no single blood test that says "yes, this is PCOS." Instead, doctors look at a combination of features — and the Rotterdam criteria are the framework most commonly used to do that.
The Three Key Features
The Rotterdam criteria focus on three features. A diagnosis is generally considered when at least two of the three are present:
- Irregular or absent ovulation — often reflected in irregular, infrequent, or missing periods.
- Signs of elevated androgens — either clinical signs such as excess hair growth or acne, or biochemical signs detected through blood tests.
- Polycystic ovaries on ultrasound — a higher-than-typical number of small follicles, or increased ovarian volume.
Because only two of three are needed, PCOS can look quite different from one woman to another. One woman might have irregular cycles and raised androgens but normal-appearing ovaries; another might have a different combination entirely.
Why "Two of Three" Matters
This flexibility is a strength, because PCOS is genuinely varied — but it also explains why the condition is sometimes confusing. For example, having polycystic-appearing ovaries on a scan alone does not mean you have PCOS, since this finding can occur in women without the syndrome. Likewise, irregular periods have many possible causes. The criteria are designed to be interpreted by a clinician, not applied to yourself from a single scan or symptom.
Ruling Other Things Out First
A crucial part of using the Rotterdam criteria is that PCOS is a diagnosis of exclusion. Before settling on PCOS, a doctor will want to make sure other conditions are not responsible for similar symptoms. These can include thyroid disorders, raised prolactin, and other hormonal conditions. This is why doctors often arrange specific blood tests as part of the work-up.
This step protects you from a misdiagnosis and ensures that anything else contributing to your symptoms is identified. It is one of the main reasons a proper medical assessment is so valuable — a checklist alone cannot do this.
What an Assessment Involves
A typical assessment may include a discussion of your menstrual history and symptoms, a review of skin and hair changes, blood tests to look at relevant hormones and rule out other causes, and sometimes an ultrasound. A doctor then brings these together and interprets them against the criteria, in the context of your individual situation.
The aim is not just to apply a label but to understand your picture so that any management plan fits you.
Why a Scan Alone Isn't a Diagnosis
A frequent source of confusion is the ultrasound finding. Having polycystic-appearing ovaries on a scan does not, by itself, mean you have PCOS — this appearance can occur in women without the syndrome. Likewise, irregular periods alone have many possible causes. This is exactly why the Rotterdam framework requires a combination of features, interpreted together, rather than any single finding.
It is also why self-diagnosis from one scan or symptom can be misleading. A doctor brings together your menstrual history, signs of elevated androgens, and where relevant the scan, and crucially rules out other conditions that can mimic PCOS, such as thyroid problems or raised prolactin. This careful, combined approach protects you from both over- and under-diagnosis. If you have been told you have polycystic ovaries and are unsure what it means, a consultation can give you an accurate, individualised picture.
When to Speak to a Doctor
Consider speaking to a doctor if you have irregular periods, signs that might point to elevated androgens such as persistent acne or excess hair growth, or if you have been told you have polycystic ovaries on a scan and want to understand what it means. A consultation can help you get a clear, individualised assessment rather than guessing.
Seek prompt medical attention for very heavy bleeding, severe pelvic pain, or any symptom that worries you.
Understanding the Rotterdam criteria helps — but only a clinician can apply them properly to your case.
Speak to a licensed doctor on Zoey. A discreet, MOH-licensed consultation lets you discuss assessment and next steps with a Singapore doctor. Start a consultation when you are ready.
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This article is for general education and is not medical advice. A consultation with a licensed doctor is required before any treatment.