How Is PCOS Diagnosed? Tests & Criteria Explained

Research shows that on average, it takes two years and visits to three different doctors for someone to get a diagnosis of polycystic ovary syndrome (PCOS), even though it’s one of the most common hormonal conditions in the UK, affecting around 1 in 10 women.

Part of the problem is that PCOS presents differently in different people. There’s no single symptom that confirms it, no single test that catches every case, and whilst the  diagnostic criteria is  clinically sound, it requires ruling out other conditions before it can be applied. Add  that to the reality that many GPs have limited time and variable knowledge of reproductive hormones,  it’s not difficult to understand why so many people spend years being told their symptoms are normal, or being tested for the wrong things.

This guide walks through exactly how PCOS is diagnosed: the criteria clinicians use, the tests involved, what the process typically looks like, and what you can do if you’re struggling to get answers.

Quick Facts

• PCOS affects around 1 in 10 women and people assigned female at birth in the UK.
• PCOS is usually diagnosed using the Rotterdam criteria: you need to meet at least two of three criteria – irregular cycles, elevated androgens, or polycystic ovarian morphology.
• Diagnosis involves a combination of blood tests (including LH, FSH, testosterone, AMH, prolactin, and thyroid hormones), pelvic ultrasound, and clinical assessment.
• Other conditions such as thyroid disorders must be ruled out before a PCOS diagnosis can be confirmed.

How is PCOS diagnosed?

PCOS is most commonly diagnosed using what’s known as the Rotterdam criteria, established by an international consensus in 2003 and last updated in 2023. To receive a PCOS diagnosis, a person must meet at least two of the following three criteria:

1. Irregular or absent menstrual cycles. This means cycles that are consistently shorter than 21 days, longer than 35 days, or absent altogether. Irregular cycles indicate that ovulation is not occurring regularly, a key feature of PCOS. According to the 2023 International Evidence-Based PCOS Guidelines, irregular cycles are defined as fewer than eight cycles per year, or cycle intervals outside the 21–35 day range, in women who are at least three years post-menarche (which is your first period).

2. Clinical or biochemical signs of high androgens (hyperandrogenism). This means either physical symptoms associated with elevated androgens such as excess facial or body hair (hirsutism), acne, or scalp hair thinning or elevated androgen levels on a blood test – typically testosterone. Importantly, you don’t need both signs of hyperangrogenism – physical signs alone, or blood results alone, can satisfy this criterion.

3. Polycystic ovarian morphology (PCOM). This refers to the appearance of the ovaries on an ultrasound scan, specifically a high number of small antral follicles (the immature follicles that house eggs) in one or both ovaries, or an increased ovarian volume. Alternatively, a high AMH (anti-Müllerian hormone) level on a blood test can be used as a marker of PCOM when an ultrasound isn’t available or appropriate.

Two out of three. That’s the threshold. Which means you can have PCOS without polycystic-looking ovaries on a scan. You can have PCOS without acne or excess hair growth. You can have PCOS with a relatively regular period. This variability is one reason why the diagnosis of PCOS is frequently missed or delayed – there’s no single presentation that fits everyone.

What tests might I need to do to get a PCOS diagnosis?

A PCOS diagnosis is built from a combination of clinical assessments, blood tests, and often an ultrasound. Here’s what each one involves.

Blood tests for PCOS diagnosis

Blood tests are central to PCOS diagnosis, both for assessing hormone levels and for ruling out other conditions that can mimic PCOS. The following are typically included in a diagnostic workup:

LH and FSH Luteinising hormone (LH) and follicle-stimulating hormone (FSH) are both made by the pituitary gland and work together to regulate the menstrual cycle. In PCOS, LH is often elevated relative to FSH, producing a raised LH:FSH ratio (typically greater than 2:1). This is one of the hormonal patterns clinicians look for in the early follicular phase, ideally tested around day 2–5 of the cycle.

Oestradiol Oestradiol (the primary form of oestrogen) is tested alongside FSH to interpret the hormonal picture correctly. High oestradiol can suppress FSH artificially, which is why these two should always be read together.

Testosterone and other androgens Testosterone and DHEAS (dehydroepiandrosterone sulphate) are tested to assess androgen levels. Elevated androgens support the hyperandrogenism criterion and help explain symptoms like excess body or facial hair and acne. 

SHBG blood test measures the level of a protein called sex hormone binding globulin (SHBG) in your blood. SHBG attaches to sex hormones such as testosterone and estrogen and helps control how much of these hormones are active  in the tissues of your body and to understand how testosterone and oestrogen are working in the body.

AMH (anti-Müllerian hormone) AMH is made by the antral follicles in the ovaries (early stage follicles that haven’t been selected for ovulation yet) and reflects the size of your egg reserve. In PCOS, AMH is often significantly elevated becausethere is a high number of small follicles stuck at different stages of development. A high AMH can serve as a marker of polycystic ovarian morphology in clinical settings, particularly when an ultrasound is unavailable. AMH doesn’t fluctuate dramatically across the cycle but is ideally tested on day 3 of the cycle for consistency.

Thyroid function tests (TSH and free T4) Both an underactive and overactive thyroid can cause irregular cycles, weight changes, and fatigue that closely resemble PCOS symptoms. Ruling out thyroid issues is a standard part of the diagnostic process.

Prolactin Elevated prolactin (hyperprolactinaemia) can also disrupt the menstrual cycle and cause irregular or absent periods. Testing prolactin helps exclude this as an alternative explanation for cycle irregularity.

Glucose and insulin / HbA1c Because insulin resistance affects a lot of people with PCOS and significantly impacts its management, assessing metabolic markers such as fasting glucose or HbA1c is an important part of a thorough diagnostic workup.

These tests are ideally taken in the early follicular phase, between days 2–5 of the menstrual cycle, when cycling hormones like LH, FSH, and oestradiol are at their baseline. If your cycles are very irregular, your doctor may advise testing at a specific point or to simply proceed whenever possible.

Hertility’s Advanced At-home Hormone & Fertility Test checks for these markers including LH, FSH, oestradiol, testosterone, AMH, prolactin, and thyroid hormones, from a single finger-prick blood sample at home. Results come with a clinician-reviewed report that highlights any patterns consistent with PCOS and gives you  next steps, with expert guidance at every stage.

Pelvic ultrasound for PCOS diagnosis

An internal or transvaginal ultrasound may also be recommended to confirm your diagnosis as it is the most accurate way to assess ovarian morphology. It allows a doctor to directly count the number of follicles in the ovary and measure ovarian volume. The threshold for polycystic ovarian morphology on ultrasound was updated in the 2023 international guidelines to 20 or more follicles per ovary, or an ovarian volume greater than 10ml in at least one ovary.

A transabdominal ultrasound (through the abdomen rather than internally) can be used as an alternative, though it’s generally considered less accurate for follicle counting. For people who haven’t been sexually active, transabdominal ultrasound is typically preferred.

It’s worth noting that ultrasound is not always performed as a first step in the UK NHS pathway, particularly in younger people, where a blood-based picture alongside symptoms may be considered sufficient to reach a diagnosis.

Can’t get a scan quickly on the NHS? If you’ve had your Hertility hormone test and your results suggest PCOS, our clinical team can refer you directly for a pelvic ultrasound, no GP referral required.

Physical examination and clinical history during PCOS diagnosis

Blood tests and scans tell part of the story, but your clinical history fills in the rest. A thorough assessment typically covers five areas:

🩸Your menstrual history – How long are your cycles? Are they regular? Have things changed? Have you ever had no period at all? Tracking this in advance, even a few months of cycle data makes this conversation far more productive.

🧴Signs of elevated androgens  – Do you have excess facial or body hair, persistent acne (especially around the jaw and chin), or scalp hair thinning? These are the visible signs of elevated androgens.

⚖️ Metabolic markers – including BMI and waist circumference are recorded because weight gain especially around the abdomen, is common in PCOS and has a direct bearing on insulin resistance and long-term health risk.

🔍 Skin changes –  Acanthosis nigricans, patches of darker, thickened skin that tend to appear around the neck, armpits, or groin is a visible sign of insulin resistance 

👨‍👩‍👧 Family history – Growing amounts of research show that PCOS might have a genetic component. A mum, sister, or aunt with PCOS, irregular cycles, or type 2 diabetes is worth mentioning.

Conditions that need to be ruled out
while getting a PCOS diagnosis

Before a PCOS diagnosis can be confirmed, clinicians must exclude other conditions that can produce similar symptoms. This is a key reason the diagnostic process takes time and why a good clinician will run a broader panel than just the obvious markers.

Conditions commonly excluded include:

• Thyroid disorders – both hypothyroidism and hyperthyroidism can disrupt cycle regularity.
• Hyperprolactinaemia – elevated prolactin can also disrupt cycle regularity.
• Congenital adrenal hyperplasia (CAH) – a condition affecting adrenal hormone production that can cause elevated androgens and irregular cycles
• Cushing’s syndrome – rare, but causes elevated cortisol that can disrupt hormonal balance
• Androgen-secreting tumours – rare, but should be considered when testosterone levels are very markedly elevated

The standard blood panel for PCOS investigation will typically include tests to exclude these, meaning the diagnostic workup serves a dual purpose: confirming PCOS while ruling out other explanations.

How Can Hertility Help You Get a PCOS Diagnosis?

Getting a PCOS diagnosis can often feel fragmented, blood tests in one place, scans in another, and long waits to speak to a specialist. Hertility is designed to bring these steps together into one streamlined, clinically guided pathway.

While PCOS diagnosis still follows established medical criteria, Hertility can support you through every stage of that process, from initial testing to clinical diagnosis and ongoing management.

1. Comprehensive Hormone Testing at Home

PCOS is fundamentally a hormonal condition, and blood testing is one of the first steps in identifying it.

Hertility’s Advanced At-home Hormone & Fertility Test measures key hormones linked to PCOS, including androgens (like testosterone), LH and FSH, AMH, and other markers such as thyroid hormones and prolactin. These results help identify patterns consistent with PCOS and rule out other conditions that can present with similar symptoms. Rather than waiting months for initial investigations, this gives you an early, clinically relevant starting point.

2. Ultrasound Scans to Complete the Picture

A diagnosis of PCOS isn’t based on blood tests alone. One of the core diagnostic criteria is the presence of polycystic ovarian morphology on ultrasound.

Through Hertility, you can access ultrasound scans, allowing clinicians to assess ovarian appearance alongside your hormone results and symptoms. This is a critical step in confirming whether you meet the diagnostic criteria.

3. Access to Expert Guidance

We don’t believe in just giving you numbers, through Hertility, you have access to experienced fertility advisors, GPs and gynaecologists who review your results in full context. This includes your hormone profile, ultrasound findings, symptoms, and menstrual cycle history, all of which are essential in building an accurate picture of your reproductive health.

This means you’re not left interpreting results on your own; you have specialist input guiding the process.. This joined-up, specialist-led approach helps ensure that your results are not only understood, but translated into a clear diagnosis and next steps, with expert guidance at every stage.

4. Ongoing Support, Including Nutrition and Lifestyle

A PCOS diagnosis isn’t the end of the journey – it’s the start of managing the condition.

Hertility also offers access to nutritionists and clinical guidance to help you:

• Manage symptoms like insulin resistance and weight changes
• Support ovulation and cycle regularity
• Improve long-term metabolic and reproductive health

This is especially important because PCOS is not just a reproductive condition, it also affects metabolic health over time.

Hertility doesn’t just flag possible PCOS, it can support you through the full diagnostic pathway, combining hormone testing, ultrasound scans, and specialist care in one place.

For many people, this means faster answers, clearer next steps, and a more confident diagnosis, without navigating the system alone.

Frequently asked questions

Can you have PCOS without cysts on your ovaries?
Yes. Despite the name, “polycystic” ovaries don’t mean you have cysts, and you don’t need a polycystic appearance on a scan to be diagnosed. Under the Rotterdam criteria, you only need to meet two of three features. Many people with PCOS are diagnosed on the basis of irregular cycles and elevated androgens alone, with no ultrasound findings at all.

Can you have PCOS with regular periods?
It’s less common, but yes. Some people with PCOS have cycles that appear regular in length but where ovulation isn’t actually occurring consistently. If you have regular periods but other signs, elevated testosterone, acne, excess hair growth, or a high AMH, PCOS can still be on the table. A Hertility Advanced Hormone & Fertility Test and scan can help clarify the picture.

What is the Rotterdam criteria?
The Rotterdam criteria is the international diagnostic framework for PCOS. It requires at least two of three features: irregular or absent periods, clinical or biochemical signs of elevated androgens (hyperandrogenism), and polycystic ovarian morphology (on ultrasound or via a high AMH). It was established in 2003 and updated in the 2023 International Evidence-Based PCOS Guidelines.

Is a pelvic ultrasound always required for PCOS diagnosis?
Not always. In many clinical settings, including NHS practice, a diagnosis can be reached through blood results and clinical history alone if two of the three Rotterdam criteria are clearly met. That said, an ultrasound provides valuable additional information, particularly for treatment planning. Hertility can refer you for a pelvic ultrasound if your hormone results suggest PCOS and a scan would complete the diagnostic picture.

Does PCOS affect fertility?
PCOS is one of the most common causes of irregular or absent ovulation, which can make conception more difficult, but the majority of people with PCOS can conceive, often with relatively straightforward support. For more on this, see our guide on trying to conceive with PCOS.

References:

Helena Teede et al. International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome 2023. Monash University. https://doi.org/10.26180/24003834.v1 

Khan MJ, Ullah A, Basit S. Genetic Basis of Polycystic Ovary Syndrome (PCOS): Current Perspectives. Appl Clin Genet. 2019 Dec 24;12:249-260. doi: 10.2147/TACG.S200341. PMID: 31920361; PMCID: PMC6935309. 

Melanie Gibson-Helm, Helena Teede, Andrea Dunaif, Anuja Dokras, Delayed Diagnosis and a Lack of Information Associated With Dissatisfaction in Women With Polycystic Ovary Syndrome, The Journal of Clinical Endocrinology & Metabolism, Volume 102, Issue 2, 1 February 2017, Pages 604–612, https://doi.org/10.1210/jc.2016-2963

Rotterdam ESHRE/ASRM-Sponsored PCOS consensus workshop group. Revised 2003 consensus on diagnostic criteria and long-term health risks related to polycystic ovary syndrome. Fertil Steril 2004a;81:19–25.

Rui Wang, Ben Willem J. Mol, The Rotterdam criteria for polycystic ovary syndrome: evidence-based criteria?, Human Reproduction, Volume 32, Issue 2, 1 February 2017, Pages 261–264, https://doi.org/10.1093/humrep/dew287

Szkodziak, P., Szkodziak, F., Trzeciak, K. et al. Insulin resistance in polycystic ovary syndrome phenotypes and the vicious cycle model in its etiology. Sci Rep 15, 42649 (2025). https://doi.org/10.1038/s41598-025-26718-2