How is PCOS Diagnosed? Rotterdam Criteria, Tests & What to Expect

Getting a PCOS diagnosis can be a long and frustrating process. The average woman waits more than 2 years and sees 3 or more healthcare professionals before receiving a diagnosis, and 85% are dissatisfied with the information they receive along the way. Understanding how diagnosis works, which tests to request, and what to bring to your appointment can make a meaningful difference in how quickly and smoothly the process goes.

The Rotterdam criteria

The Rotterdam criteria are the current international standard for diagnosing PCOS, established in 2003 and reaffirmed in the 2018 ESHRE/ASRM International Evidence-Based Guideline. A diagnosis requires the presence of at least 2 of the following 3 features, after other conditions that cause similar symptoms have been excluded.

Feature 1: Irregular or absent ovulation. This is typically assessed through your menstrual history. Clinically, this means cycles shorter than 21 days or longer than 35 days, fewer than 9 periods per year (oligomenorrhoea), or absence of periods for 3 or more consecutive months (amenorrhoea). If your cycles are variable but you are unsure whether they qualify as “irregular,” tracking them over several months provides the clearest picture for your doctor.

Feature 2: Hyperandrogenism (elevated androgens). This can be assessed in two ways. Clinical hyperandrogenism refers to visible symptoms: acne (particularly along the jawline and chin), hirsutism (excess facial or body hair), or androgenic hair loss (thinning on the scalp). Biochemical hyperandrogenism is confirmed through blood tests showing elevated total testosterone, free testosterone, DHEAS, or Free Androgen Index (FAI). Clinical symptoms can suggest hyperandrogenism, but blood tests provide the definitive confirmation.

Feature 3: Polycystic ovarian morphology (PCOM). This is identified on transvaginal or transabdominal ultrasound. The criteria are 12 or more follicles measuring 2 to 9mm in diameter in at least one ovary, or an ovarian volume greater than 10ml. Not all women with PCOS have this feature, and polycystic-appearing ovaries can also occur in women without PCOS.

You need 2 of these 3 features, not all three. This is why PCOS has four distinct phenotypes, each representing a different combination.

What tests should you request?

If you suspect PCOS, the following blood tests are relevant to the diagnostic workup. Not every doctor will order all of them unprompted, so it can be helpful to know what to ask for.

Core hormone panel:
LH and FSH (an elevated LH to FSH ratio is common in PCOS, though not required for diagnosis), total testosterone, free testosterone or Free Androgen Index (FAI = total testosterone / SHBG x 100), SHBG (sex hormone binding globulin, often low in PCOS, which increases bioavailable androgens), and DHEAS (an adrenal androgen marker that helps distinguish ovarian from adrenal sources of hyperandrogenism).

Metabolic panel:
Fasting insulin (a direct marker of insulin resistance), fasting glucose (metabolic baseline), HOMA-IR (a calculated insulin resistance index using fasting insulin and glucose), HbA1c (long-term glucose control, standard diabetes screening), and a lipid panel (total cholesterol, LDL, HDL, triglycerides) for cardiovascular risk assessment.

Exclusion tests (essential):
TSH (to rule out thyroid disorders, which can mimic PCOS symptoms), prolactin (to rule out hyperprolactinaemia), and 17-hydroxyprogesterone (to rule out congenital adrenal hyperplasia, which mimics PCOS). The Endocrine Society guidelines specifically recommend these exclusion tests as part of the PCOS workup.

Additional tests your doctor may consider:
AMH (anti-Mullerian hormone, often elevated in PCOS and reflective of antral follicle count), Vitamin D (commonly deficient in PCOS), liver function tests (ALT, AST, GGT, relevant because NAFLD/MASLD is a recognised PCOS comorbidity), and anti-TPO antibodies (Hashimoto's thyroiditis has an elevated prevalence in women with PCOS).

Pelvic ultrasound:
To assess ovarian morphology. A transvaginal ultrasound provides the best image quality if you are comfortable with the procedure. A transabdominal ultrasound is an alternative.

When to get tested

Blood tests for hormones are most informative when drawn at the right point in your cycle. If you have relatively regular cycles, days 2 to 5 of your cycle (counting from the first day of your period) is the standard window for hormone testing. If your cycles are irregular or absent, testing can be done at any time, and your doctor may ask you to return for a repeat test to confirm results.

Fasting insulin and glucose require a fasting blood draw (typically 8 to 12 hours without food). If your doctor orders these alongside hormone tests, plan for a morning appointment.

What to expect at your appointment

The diagnostic process for PCOS typically involves a medical history review, a physical examination, blood tests, and potentially an ultrasound. Depending on your healthcare system and the specialist you see, this may happen across one visit or several.

Medical history. Your doctor will ask about your menstrual cycle (regularity, length, heaviness), any visible symptoms (acne, excess hair growth, hair loss), weight history, family history of PCOS or diabetes, and your fertility goals if relevant.

Physical examination. Your doctor may assess for clinical signs of hyperandrogenism (hirsutism scoring, acne, hair thinning) and insulin resistance (acanthosis nigricans, weight distribution).

Blood tests. As described above. Results typically take a few days to a week.

Ultrasound. If needed to assess ovarian morphology. This may be ordered at the first visit or after blood results are reviewed.

Preparing for the appointment

The more data you bring to your appointment, the more productive it will be. A verbal recollection of “my periods are irregular” is far less useful to a clinician than 3 to 6 months of tracked cycle data with dates and lengths.

Before your appointment, it helps to prepare: a record of your last several periods (dates, lengths, and any notable symptoms), a list of the symptoms you experience with approximate timing and severity, any relevant family history (PCOS, diabetes, thyroid conditions in close relatives), a list of current medications and supplements, and the specific tests you would like to discuss if they have not been ordered.

For a detailed guide on how to structure your appointment preparation across different specialist types, see our appointment preparation guide.

What if your doctor dismisses your concerns?

This is unfortunately common. If your doctor does not take your symptoms seriously, does not order the relevant tests, or tells you to “just lose weight” without investigating further, you have the right to seek a second opinion.

When seeking another opinion, it helps to bring structured documentation of your symptoms rather than starting from scratch. A clear record of what symptoms you have experienced, when, and what has already been tested or ruled out gives the next doctor a head start and demonstrates that your concerns are grounded in data.

Alaia's Building My Case mode is designed specifically for this situation. It maps your logged symptoms to the Rotterdam criteria and generates a structured evidence report that summarises your symptom history, cycle data, and any test results you have logged, giving you a clear document to bring to your next appointment. For women who have been dismissed, Second Opinion Preparation mode provides structured guidance on what to bring, what to say, and which specialist type to try next.

After diagnosis: what comes next

Receiving a PCOS diagnosis can bring a mix of emotions: relief at finally having an answer, frustration at the time it took, and uncertainty about what to do next. Here are the immediate next steps that matter most.

Understand your phenotype. Ask your doctor which Rotterdam criteria you meet. This tells you your phenotype and helps guide which management approaches are most relevant. For more on this, read about PCOS types.

Get baseline metabolic screening. If it was not already done during diagnosis, request fasting insulin, fasting glucose, HbA1c, and a lipid panel. These establish your metabolic baseline and guide monitoring going forward.

Start tracking. The more consistently you track your symptoms, cycle, and any treatments, the better equipped you and your care team will be to assess what is working and what needs adjustment.

Build your care team. PCOS management may involve a gynaecologist, endocrinologist, dermatologist, nutritionist, and mental health professional depending on your symptoms. You do not need all of them immediately, but knowing which specialists are relevant to your situation helps you plan.

Learn about your condition. Evidence-based education makes a measurable difference. For a comprehensive overview, see our main PCOS guide.

This content is for informational purposes only. Always consult a qualified healthcare provider for diagnosis and treatment decisions.

Sources: 2018 ESHRE/ASRM International Evidence-Based Guideline; Endocrine Society Clinical Practice Guideline; Gibson-Helm et al., JCEM, 2017; WHO PCOS Fact Sheet (2024).