Blood Workup for PCOS: UK Tests Explained

A blood workup for PCOS is a key part of diagnosing polycystic ovary syndrome and ruling out conditions that can mimic it. In the UK, GPs typically request a panel of reproductive hormones, metabolic markers and thyroid function tests, interpreted alongside your symptoms and menstrual history. Because no single result confirms PCOS on its own, results are always reviewed as part of the broader clinical picture, which may also include a pelvic ultrasound. This article explains which blood tests are included, how results are interpreted, what additional investigations your GP may arrange, and what happens once your results come back.

What blood tests are used to diagnose PCOS in the UK?

A PCOS blood workup in the UK includes reproductive hormones, metabolic markers and thyroid function tests, used alongside clinical assessment and pelvic ultrasound to apply the Rotterdam diagnostic criteria.

A PCOS blood workup in the UK typically includes tests for reproductive hormones, metabolic markers and thyroid function, used alongside clinical assessment and, where appropriate, pelvic ultrasound to reach a diagnosis. Polycystic ovary syndrome (PCOS) is diagnosed using the Rotterdam criteria, which require at least two of three features: irregular ovulation, clinical or biochemical signs of excess androgens, and polycystic-appearing ovaries on ultrasound.^[1][3] Because only two of the three features are needed, a diagnosis can be reached without ultrasound if both other criteria are clearly met. Blood tests contribute to the biochemical androgen assessment and help rule out other conditions that can mimic PCOS.

Your GP will usually request blood tests, often taken on days two to five of your menstrual cycle where possible, as hormone levels fluctuate throughout the cycle. Some tests, such as fasting glucose and lipids, require you to fast beforehand; most hormone tests, including TSH, prolactin, testosterone and SHBG, do not routinely require fasting. Your GP will advise you on preparation before your appointment. A pregnancy test (urine or serum hCG) is also typically arranged at the outset to exclude pregnancy as a cause of irregular or absent periods before other investigations proceed.

No single blood marker confirms PCOS on its own, so results are always interpreted alongside your symptoms, menstrual history and, where appropriate, ultrasound findings. In adolescents within the first two years after their first period, ultrasound is generally not recommended as a diagnostic tool because polycystic-appearing ovaries are common in this age group and do not carry the same significance; diagnosis in younger people requires careful specialist assessment.^[19][20]

Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online consultations with prescriber review and pharmacist support, and is one option for people seeking guidance on next steps after an initial GP assessment. Accessing a structured investigation pathway through your GP or a specialist remains the recommended starting point for a formal PCOS diagnosis.

Which hormones and markers does a PCOS blood panel check?

A standard PCOS blood panel checks LH, FSH, testosterone, SHBG, prolactin, TSH and glycaemic markers; each serves a specific diagnostic or exclusionary purpose within the overall workup.

A standard PCOS blood panel checks several hormones and metabolic markers, including luteinising hormone (LH), follicle-stimulating hormone (FSH), testosterone, sex hormone-binding globulin (SHBG), prolactin, thyroid-stimulating hormone (TSH), and markers of glycaemic status. Each marker serves a specific diagnostic or exclusionary purpose within the overall workup.

Key components of a typical PCOS blood panel include:

• LH and FSH: An elevated LH to FSH ratio (often cited as greater than 2:1) can support a PCOS diagnosis, though this finding is not present in all cases and is not required under the Rotterdam criteria.^[1][24]

• Total and free testosterone: Raised total testosterone or a low SHBG (which increases free androgen availability) provides biochemical evidence of hyperandrogenism, one of the core diagnostic features. Because female testosterone levels are low, assay accuracy matters; where available, liquid chromatography-mass spectrometry (LC-MS/MS) is preferred, and results near the upper reference limit should be interpreted alongside clinical signs.^[9]

• DHEAS and androstenedione: Dehydroepiandrosterone sulfate (DHEAS) and androstenedione are androgens that may be measured in specialist settings to help characterise whether excess androgen production is primarily adrenal or ovarian in origin.

• SHBG: Low SHBG amplifies the effect of circulating androgens and is commonly reduced in PCOS, particularly in those with insulin resistance.

• Prolactin: Elevated prolactin can cause irregular periods independently of PCOS and must be excluded.

• TSH: Thyroid dysfunction, both overactive and underactive, can disrupt menstrual cycles and is routinely screened for.

• Glycaemic assessment: HbA1c and, where indicated by risk factors such as raised BMI, ethnicity or family history, an oral glucose tolerance test (OGTT) are the approaches most consistently recommended in UK practice for screening for impaired glucose regulation or type 2 diabetes. Fasting insulin and HOMA-IR calculations are used in some specialist settings to assess insulin resistance but are not routinely standardised across NHS laboratories and are not required for diagnosis.^[1][2]

Anti-Mullerian hormone (AMH) is increasingly used in specialist settings as a marker of ovarian follicle count, and raised AMH levels are associated with PCOS.^[24][25] However, assay methods and reference thresholds vary between laboratories, and AMH is not yet part of all standard NHS panels; its use and interpretation should be guided by a specialist.

How do doctors interpret PCOS blood test results?

Doctors interpret PCOS blood results in the context of the full clinical picture; no single abnormal value is diagnostic, and hormone levels are reviewed alongside symptoms such as hirsutism, acne and irregular periods.

Doctors interpret PCOS blood test results in the context of the full clinical picture rather than treating any single abnormal value as diagnostic on its own. Hormone levels vary with age, body weight, cycle day and laboratory reference ranges, so results are always reviewed alongside symptoms such as irregular periods, acne, excess hair growth (hirsutism) and scalp hair thinning.

A raised total testosterone or free androgen index, combined with a low SHBG, supports biochemical hyperandrogenism. However, testosterone levels in PCOS are often only mildly elevated and may fall within the upper end of the laboratory's normal range. In this situation, clinical signs of androgen excess carry significant diagnostic weight. Conversely, a normal testosterone result does not exclude PCOS if other criteria are met.

The LH to FSH ratio is a supportive finding rather than a diagnostic requirement. Some laboratories no longer routinely report this ratio, and its absence from a result does not indicate an incomplete test. Prolactin and TSH results are reviewed to exclude hyperprolactinaemia and thyroid disease respectively, both of which can independently cause menstrual irregularity.

If prolactin is raised, your GP will consider whether any current medicines (such as antipsychotics or certain antiemetics) could be contributing, and may arrange a repeat test. Persistent or markedly elevated prolactin, or prolactin elevation accompanied by headaches or visual disturbance, warrants prompt referral to an endocrinologist to exclude a pituitary cause.^[8]

You should seek urgent assessment if you experience rapidly progressive symptoms of androgen excess, such as deepening of the voice, significant clitoral enlargement, or very rapid onset of hirsutism. These features, or a markedly elevated total testosterone or DHEAS, may indicate an androgen-secreting tumour rather than PCOS and require urgent specialist investigation. Your GP or gynaecologist will explain which results fall outside the reference range and what they mean for your individual situation, and will refer you to an endocrinologist or gynaecologist if specialist input is needed.

What else might your GP test for alongside PCOS bloods?

GPs may also request fasting lipids, HbA1c or OGTT, 17-hydroxyprogesterone, cortisol and liver function tests to assess metabolic risk and exclude conditions such as congenital adrenal hyperplasia or Cushing's syndrome.

Alongside the core PCOS hormone panel, your GP may request additional tests to assess cardiovascular and metabolic risk, screen for related conditions, or investigate symptoms that could have an alternative cause. PCOS is associated with a higher long-term risk of type 2 diabetes, dyslipidaemia and hypertension, so a broader metabolic screen is clinically appropriate at diagnosis.

Additional tests and assessments your GP may arrange include:

• Fasting lipid profile: Cholesterol and triglyceride levels are often checked because dyslipidaemia is more common in people with PCOS, particularly those with insulin resistance or obesity.

• HbA1c and/or OGTT: To screen for impaired glucose regulation or type 2 diabetes, in line with NICE guidance on metabolic risk in PCOS. The choice between HbA1c and OGTT is guided by individual risk factors including BMI, ethnicity and family history.

• 17-hydroxyprogesterone (17-OHP): This is measured to exclude congenital adrenal hyperplasia (CAH), a condition that can cause androgen excess and irregular periods and is sometimes mistaken for PCOS.^[10][11]

• Cortisol: If Cushing's syndrome is suspected based on symptoms such as central weight gain, stretch marks or easy bruising, a 24-hour urinary cortisol or overnight dexamethasone suppression test may be arranged.

• Full blood count (FBC): Useful if heavy or prolonged periods are reported, to check for iron-deficiency anaemia.

• Liver function tests (LFTs): People with PCOS and metabolic risk factors have a higher prevalence of non-alcoholic fatty liver disease (NAFLD), and an ALT measurement may be included in the initial screen where this risk is present.^[14][15]

• BMI and waist circumference: These are measured as part of baseline cardiometabolic risk assessment and help guide decisions about lifestyle intervention and further investigation.

• Blood pressure measurement: Hypertension is more prevalent in PCOS and should be assessed at the time of diagnosis.

Your GP may also ask about symptoms of obstructive sleep apnoea, such as loud snoring, witnessed pauses in breathing or excessive daytime sleepiness, as this condition is more common in people with PCOS and obesity and may warrant onward assessment.^[16][17] A pelvic ultrasound scan may be arranged where it would add diagnostic information, though it is not mandatory if two other Rotterdam criteria are already met.

What happens after your PCOS blood workup comes back?

After results return, your GP will confirm or exclude a PCOS diagnosis and discuss a management plan covering lifestyle measures, cycle regulation, metabolic risk reduction and, where relevant, fertility support.

After your PCOS blood workup returns, your GP will review the results alongside your symptoms and any imaging findings to confirm or exclude a diagnosis and discuss a management plan. PCOS has no single curative treatment, but its symptoms and associated health risks are manageable with a combination of lifestyle measures and, where appropriate, medication.

Lifestyle intervention, including a balanced diet and regular physical activity, is recommended as a first-line approach for all people with PCOS, not only those with a raised BMI. Even modest improvements in diet and activity levels can benefit insulin sensitivity, menstrual regularity and cardiovascular risk regardless of weight.

If a diagnosis of PCOS is confirmed, management is guided by your individual priorities, which may include regulating your menstrual cycle, managing acne or hirsutism, supporting fertility, or reducing long-term metabolic risk. Medications your GP or specialist may discuss include:

• Combined oral contraceptive pill: Commonly used to regulate periods and reduce androgen-related symptoms such as acne and excess hair.

• Cyclical progestogen or a levonorgestrel-releasing intrauterine system (LNG-IUS): For people with infrequent periods, protecting the endometrium from the effects of prolonged unopposed oestrogen is important; your GP or specialist will advise on the most suitable approach.

• Metformin: May be considered for metabolic management, particularly where insulin resistance or impaired glucose regulation is identified, in line with NICE guidance.^[6][7]

• Eflornithine cream or referral for hair removal: For hirsutism that does not respond to hormonal treatment.

• Ovulation induction for fertility: Current NICE and ESHRE guidance supports letrozole as a first-line option for ovulation induction in anovulatory PCOS.^[26][27] Clomifene has historically been used and may still be offered in some settings. If you have been trying to conceive without success for 12 months (or sooner if you are older or known to have anovulation), referral to a fertility specialist is appropriate.

Ongoing monitoring after diagnosis typically includes blood pressure assessment at least annually, glycaemic status review at diagnosis and at regular intervals thereafter (frequency guided by individual risk), and lipid reassessment according to cardiovascular risk. Where NAFLD or sleep apnoea risk is identified, your GP will advise on further evaluation.

You should contact your GP if you develop new or worsening symptoms, if your periods become very heavy or painful, or if you have concerns about fertility. PCOS is a long-term condition and your management plan may need to be reviewed as your circumstances and priorities change.

Scientific References

1. Polycystic ovary syndrome: assessment and management (GID-NG10436 supporting documentation – biochemical hyperandrogenism).
2. Polycystic ovary syndrome: assessment and management – glycaemic status supporting documentation.
3. PMOS guideline (GID-NG10436 document 450).
4. Polyendocrine Metabolic Ovarian Syndrome (PMOS) – guideline in development.
5. Polyendocrine metabolic ovarian syndrome (PMOS).
6. Polycystic ovary syndrome: metformin in women not planning pregnancy (ESUOM6) – patient information.
7. Polycystic ovary syndrome: metformin in women not planning pregnancy (ESUOM6) – full resource.
8. Fertility problems: assessment and treatment – evidence review 6 (NG257).
9. Evaluating the diagnostic accuracy of androgen measurement in polycystic ovary syndrome: a systematic review and diagnostic meta-analysis to inform evidence-based guidelines.
10. Steroid Screening Tools Differentiating Nonclassical Congenital Adrenal Hyperplasia from PCOS.
11. Using machine learning to discriminate non-classical 21-hydroxylase deficiency from polycystic ovary syndrome: an external validation study.
12. Hyperandrogenism in polycystic ovary syndrome and adrenal hyperplasia: finding differences to make a specific diagnosis.
13. Establishing a new screening 17-hydroxyprogesterone cut-off value and evaluation of the reliability of the long intramuscular ACTH stimulation test in the diagnosis of nonclassical congenital adrenal hyperplasia.
14. Non-Alcoholic Fatty Liver Disease in Patients with Polycystic Ovary Syndrome.
15. Unraveling the Interplay between Nonalcoholic Fatty Liver Disease and Polycystic Ovary Syndrome in Adolescents: Pathogenesis, Prevalence, and Management Strategies.
16. Prevalence of Obstructive Sleep Apnea in Patients With Polycystic Ovary Syndrome: A Systematic Review and Meta-Analysis.
17. Obstructive sleep apnea syndrome in polycystic ovary syndrome: a systematic review and meta-analysis.
18. Sex Hormones, Sex Hormone-Binding Globulin and Sleep Problems in Females With Polycystic Ovary Syndrome: A Systematic Review and Meta-Analysis.
19. The value of anti-Mullerian hormone for diagnosing polycystic ovary syndrome in adolescents: a case-control study based on an epidemiological survey.
20. Adolescents diagnosed with polycystic ovary syndrome under the Rotterdam criteria but not meeting the diagnosis under the updated guideline.
21. PCOS in Adolescents – Ongoing Riddles in Diagnosis and Treatment.
22. Rare Conditions of Hyperandrogenism Through Lifespan: A Case Series.
23. Differential diagnosis of hyperandrogenism in women with polycystic ovary syndrome.
24. Function of anti-Müllerian hormone (AMH), gonadotropins and FSHR rs6166 genetic variant in the pathogenesis and diagnostic assessment of polycystic ovary syndrome.
25. Serum phoenixin-14 and phoenixin-20 concentrations in polycystic ovary syndrome: Associations with anti-Müllerian hormone and diagnostic utility.
26. Efficacy of sequential letrozole and gonadotropin therapy for ovulation induction in women with polycystic ovary syndrome: a systematic review and meta-analysis.
27. Efficacy of letrozole versus clomiphene citrate on ovulation induction in patients with polycystic ovarian syndrome.
28. Letrozole versus clomiphene citrate for ovulation induction in anovulatory women with polycystic ovarian syndrome: A randomized controlled trial.

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