PCOS: What the 2023 Guidelines Changed and What Blood Tests Can Tell You

Polycystic ovary syndrome is the most common hormonal condition in women of reproductive age, affecting between 10 and 13% of the global female population [Teede et al., 2023]. Despite that prevalence, it remains one of the most underdiagnosed and poorly understood conditions in primary care.

A landmark survey of 1,385 women across 32 countries found that more than a third waited over two years for a diagnosis, and nearly half saw three or more clinicians before getting one [Gibson-Helm et al., 2017]. That delay matters. PCOS isn't just a reproductive condition. It carries long-term metabolic and psychological consequences that are far easier to manage when identified early.

What Is PCOS?

Polycystic ovary syndrome (PCOS) is a hormonal condition characterised by a combination of features. The 2023 International Evidence-based Guideline, endorsed by 39 professional societies across 71 countries, uses the Rotterdam criteria to define diagnosis. You need at least two of the following three features [Teede et al., 2023]:

• Irregular or absent periods (oligo-anovulation), indicating that ovulation isn't happening reliably

• Clinical or biochemical hyperandrogenism, meaning either visible signs of excess androgens (such as acne, excess facial or body hair, or scalp hair thinning) or elevated androgen levels on a blood test

• Polycystic ovarian morphology, identified either on ultrasound (12 or more follicles per ovary, or an ovarian volume above 10ml) or through an elevated anti-Mullerian hormone (AMH) level

An important caveat on AMH: the 2023 guideline specifies that AMH should only be used as an alternative to ultrasound for diagnosing polycystic ovarian morphology in adults. It should not be used in adolescents, because AMH levels in younger women naturally overlap with normal pubertal development and multi-follicular ovaries. If you're under 18, the diagnostic pathway is different and requires specialist input.

Other conditions that can mimic PCOS, including thyroid disorders, congenital adrenal hyperplasia, and hyperprolactinaemia, must be excluded before the diagnosis is made.

Symptoms You Might Recognise

PCOS can present very differently from person to person. Common features include:

• Irregular, infrequent, or absent periods

• Excess facial or body hair growth (hirsutism)

• Persistent acne, particularly along the jawline

• Scalp hair thinning

• Difficulty losing weight, particularly around the midsection

• Fatigue and low energy

• Low mood, anxiety, or difficulty concentrating

• Difficulty conceiving

Not everyone with PCOS will have all of these. Some women have regular periods but significant hyperandrogenism. Others have very irregular cycles but no visible androgen excess. The condition exists on a spectrum, which is part of why it's so often missed.

The Metabolic Side of PCOS

This is the part that often gets overlooked. PCOS isn't only about periods and fertility. It carries genuine metabolic consequences.

Insulin resistance is present in a significant proportion of women with PCOS, including some who are not overweight. When cells respond less efficiently to insulin, the pancreas compensates by producing more. This excess insulin stimulates the ovaries to produce more testosterone, worsening the hormonal imbalance, and simultaneously promotes fat storage, particularly around the abdomen.

The relationship between PCOS and type 2 diabetes is well established. Current meta-analyses indicate that women with PCOS have approximately a 3-fold higher risk of developing type 2 diabetes compared to women without the condition, with the risk being most pronounced in those who are also overweight or obese [Anagnostis et al., 2021]. The 2023 guideline recommends that blood sugar status should be assessed at PCOS diagnosis and reassessed every one to three years based on individual risk factors.

Cardiovascular risk is also elevated. A 2024 systematic review published in the Journal of the American Heart Association, drawing on data from over one million women, found that PCOS was associated with significantly higher rates of coronary artery disease and stroke [Tay et al., 2024]. The relationship with cardiovascular mortality was less clear and did not reach statistical significance in that analysis.

There is also a well-documented psychological burden. A meta-analysis by Cooney et al. (2017), published in Human Reproduction, found that women with PCOS were approximately 2.8 times more likely to be diagnosed with depression and 2.7 times more likely to experience anxiety disorders compared to women without the condition [Cooney et al., 2017].

Which Blood Tests Are Useful?

A blood test can't diagnose PCOS on its own. PCOS is a clinical diagnosis that requires symptom assessment, exclusion of other conditions, and often imaging or AMH testing. But the right blood panel provides critical pieces of the picture.

Hormonal markers

• Total testosterone and free androgen index (FAI) detect biochemical hyperandrogenism. SHBG is measured alongside testosterone because insulin resistance suppresses SHBG, increasing the proportion of biologically active free testosterone

• LH and FSH should ideally be measured in the early follicular phase (days 2-5) if you're still menstruating. An elevated LH-to-FSH ratio is a classic finding, though not required for diagnosis

• AMH can replace ultrasound for the morphology criterion in adults. AMH declines naturally with age, so results need age-appropriate interpretation

Metabolic markers

• HbA1c and fasting glucose to screen for insulin resistance and pre-diabetes, recommended by the 2023 guideline at diagnosis

• Fasting insulin is useful for identifying early insulin resistance before glucose levels become abnormal

• Full lipid profile to assess cardiovascular risk, particularly in those with central obesity or a family history of heart disease

Exclusion markers

• TSH and free T4 to rule out thyroid dysfunction

• Prolactin to exclude hyperprolactinaemia

• 17-hydroxyprogesterone to screen for non-classical congenital adrenal hyperplasia

Understanding Your Results

If any of your results fall outside the reference range, that doesn't automatically mean you have PCOS or any other condition.

Laboratory reference ranges represent the middle 95% of results from a healthy population. Hormone levels also fluctuate throughout the menstrual cycle, and many markers (particularly LH, FSH, and oestradiol) are only meaningful when measured at the right point in your cycle. Recent use of hormonal contraception can also significantly affect results.

Your results need to be interpreted by a clinician alongside your symptoms, your medical history, and the clinical examination findings. A blood test provides data points that inform the conversation. It doesn't provide a diagnosis in isolation.

When to See Your GP

Some situations need NHS assessment, not a private blood test:

• If you're under 18 and experiencing symptoms that could suggest PCOS, see your GP. The diagnostic criteria are different for adolescents, and AMH testing is not appropriate in this age group

• If you have very heavy or prolonged bleeding, your GP needs to assess this. Heavy bleeding in the context of irregular cycles can indicate endometrial thickening that needs investigation

• If you're trying to conceive and haven't become pregnant after 12 months (or 6 months if over 35), you need a fertility assessment through your GP

• If you're experiencing severe low mood, anxiety, or thoughts of self-harm, speak to your GP. The psychological burden of PCOS is real and treatable

How Brooksby Medical Can Help

If you suspect PCOS, if you've been told your symptoms are "just stress," or if you want a thorough hormonal and metabolic picture before your next GP appointment, a structured blood panel can give you and your doctor something concrete to work with.

The PCOS Hormone Blood Test covers the hormonal markers discussed in this article: total testosterone, SHBG, free androgen index, LH, FSH, AMH, and prolactin.

For a broader assessment that also includes metabolic screening (HbA1c, fasting glucose, insulin, full lipid profile) alongside thyroid function and 17-hydroxyprogesterone, the Women's Health Profile provides a more complete baseline.

If you're also experiencing fatigue as a dominant symptom, our briefings on thyroid function and iron deficiency may be relevant, since both conditions overlap heavily with PCOS symptoms.

Every Brooksby report is written personally by a GP who explains what your results mean together, not just whether each number is in range. If your results suggest PCOS, we'll recommend discussing them with your GP to complete the diagnostic picture.

References

1. Teede HJ, Tay CT, Laven JJE, et al. Recommendations from the 2023 international evidence-based guideline for the assessment and management of polycystic ovary syndrome. Hum Reprod. 2023;38(9):1655-1679. doi:10.1093/humrep/dead156

2. Gibson-Helm M, Teede H, Dunaif A, Dokras A. Delayed diagnosis and a lack of information associated with dissatisfaction in women with polycystic ovary syndrome. J Clin Endocrinol Metab. 2017;102(2):604-612. doi:10.1210/jc.2016-2963

3. Anagnostis P, Tarlatzis BC, Kauffman RP. Polycystic ovarian syndrome (PCOS): risk of type 2 diabetes mellitus associated with obesity: a meta-analysis. Endocrine. 2021;74(2):311-321. doi:10.1007/s12020-021-02802-5

4. Tay CT, Mousa A, Vyas A, et al. 2023 international evidence-based PCOS guideline update: insights from a systematic review and meta-analysis on elevated clinical cardiovascular disease. J Am Heart Assoc. 2024;13(16):e033572. doi:10.1161/JAHA.123.033572

5. Cooney LG, Lee I, Sammel MD, Dokras A. High prevalence of moderate and severe depressive and anxiety symptoms in polycystic ovary syndrome: a systematic review and meta-analysis. Hum Reprod. 2017;32(5):1075-1091. doi:10.1093/humrep/dex044

Written by Dr James Coleman, GP and founder of Brooksby Medical. Dr Coleman is a practising General Practitioner who founded Brooksby Medical to give patients direct access to the blood tests and clinical interpretation they need, without waiting lists.

Medically reviewed: March 2026 | Next review due: March 2027

Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Blood test results should always be interpreted by a qualified healthcare professional in the context of your individual symptoms, medical history, and clinical picture. A blood test cannot diagnose PCOS in isolation. If you have concerns about your health, please consult your GP.