Blood Tests for PCOS: Which Ones Help and Why

Polycystic ovary syndrome (PCOS) is a common hormone condition that can cause irregular or missed periods, excess hair growth, acne, weight gain and difficulty getting pregnant. The NHS website now also uses the name polyendocrine metabolic ovarian syndrome (PMOS), but because most people still know it as PCOS, that is the name we use in this guide.

There is no single blood test for PCOS. Blood tests help in three ways: they can show raised androgens (male-type hormones), they rule out other conditions that look similar, and they check your longer-term metabolic health. This guide explains which tests help and why, which test to book first, what blood tests cannot tell you and when to see a GP.

Test it in Chiswick: our Hormone Health Check blood test costs £69, with your result explained in person by a practitioner. No GP referral needed. Book this test or call 020 4515 0000. Prefer to test at home? A home finger-prick kit is also available, ask us when you enquire.

Quick answer

The key blood tests for PCOS are total testosterone with SHBG and the free androgen index, to look for raised androgens; prolactin, thyroid function and sometimes 17-OH progesterone, to rule out conditions that mimic PCOS; and HbA1c or glucose plus a cholesterol profile, because PCOS raises the risk of type 2 diabetes and heart disease. LH and FSH are often checked, but the LH to FSH ratio does not diagnose PCOS. In adults, a raised AMH can be used instead of an ultrasound scan. Diagnosis needs 2 of 3 features, never one blood result.

Blood tests that can help

Doctors diagnose PCOS using the Rotterdam criteria, updated in the 2023 international evidence-based guideline. In adults, you need at least 2 of these 3 features, once other causes have been ruled out:

• Irregular or absent ovulation: usually shown by irregular, infrequent or missed periods.
• Raised androgens: either signs such as excess hair growth or acne, or high androgen levels on a blood test.
• Polycystic ovaries: seen on an ultrasound scan or, in adults, shown by a raised AMH blood test.

In adolescents, both irregular periods and raised androgens are needed. The blood tests below help with the second and third features and with ruling out look-alike conditions.

Testosterone, SHBG and the free androgen index

The 2023 international guideline recommends total and free testosterone to check for raised androgens, with free testosterone estimated using the free androgen index (FAI). The FAI is calculated from total testosterone and SHBG (sex hormone binding globulin), the protein that carries testosterone in the blood. SHBG is often low in PCOS, which leaves more testosterone free and active, so a normal total testosterone does not always mean normal androgen activity.

Testosterone in PCOS is usually normal or only mildly raised. NHS North East London guidance advises specialist referral if testosterone is significantly raised, above 5 nmol/L or more than twice the upper limit of the laboratory range, to look for other causes. Book our Testosterone test (£49), SHBG test (£49) or Free Androgen Index (£69), which measures testosterone, SHBG and albumin and calculates the FAI. Our guides to testosterone levels in women and SHBG levels explain the numbers. The guideline adds that androstenedione and DHEA-S could also be considered; we offer a DHEA-S test (£49).

LH and FSH

Luteinising hormone (LH) and follicle stimulating hormone (FSH) are often measured, ideally on days 1 to 5 of your cycle if you are having periods. LH is often raised in PCOS, and an LH to FSH ratio above 2.5 is common, but NHS Lothian guidance notes that a raised LH and LH to FSH ratio is also commonly found in women who do not have PCOS, and that LH is not needed to make the diagnosis. Their main value is ruling out other causes: a high FSH, for example, points towards early menopause rather than PCOS. We offer LH (£49) and FSH (£49) tests, and our LH guide explains the results.

Prolactin, thyroid and 17-OH progesterone: ruling out look-alikes

The international guideline recommends ruling out thyroid disease (with TSH), high prolactin, and non-classic congenital adrenal hyperplasia (with 17-OH progesterone), because these can also cause irregular periods or excess hair. The NHS lists an overactive or underactive thyroid among the causes of missed periods. Book a Prolactin test (£49), a TSH test (£39) or the fuller Thyroid Function Check (£69). In UK practice, 17-OH Progesterone (£159) is usually added when testosterone is raised, so ask your practitioner whether you need it.

AMH (anti-Mullerian hormone)

AMH is made by small follicles in the ovaries and is often higher in PCOS. The 2023 international guideline says AMH could be used instead of an ultrasound scan to define polycystic ovaries in adults, but should not yet be used in adolescents. Neither ultrasound nor AMH is recommended for diagnosis within 8 years of your first period. A raised AMH on its own does not mean you have PCOS. Our AMH test costs £99, and our guide to AMH levels explains the result.

HbA1c, glucose and cholesterol: your metabolic health

The NHS lists type 2 diabetes, high blood pressure, cardiovascular disease and non-alcoholic fatty liver disease among the conditions PCOS can make more likely. The international guideline recommends checking blood sugar control at diagnosis and every 1 to 3 years, and a cholesterol (lipid) profile for everyone with PCOS, whatever their age and weight. It names the oral glucose tolerance test as the most accurate test; this is arranged by your GP or specialist and is not offered at our clinic, but fasting glucose and HbA1c can be used instead, with lower accuracy. Book an HbA1c test (£59), a Glucose test (£39) or a Cholesterol Profile (£49).

Fasting insulin and HOMA-IR estimate insulin resistance, but they are not diagnostic criteria and there is no agreed UK cut-off. See insulin levels explained.

Which test should I book?

• A focused start: Hormone Health Check, £69. Testosterone, SHBG, free androgen index, LH, FSH, oestradiol, progesterone and prolactin, covering the androgen tests and the main look-alike checks in one sample. It does not include thyroid or blood sugar tests.
• A broader picture: Insulin Resistance Check (HOMA-IR), £99. Fasting glucose, insulin and a calculated HOMA-IR score, for the metabolic side of PCOS. It does not include hormones or HbA1c, so it works best alongside the Hormone Health Check.
• The fullest view: Hormone and Thyroid Panel Plus, £249. Everything in the Hormone Health Check plus TSH, free T4, free T3, thyroid antibodies, AMH, HbA1c, insulin, cortisol and DHEA-S.

None of these panels includes cholesterol, so consider adding a Cholesterol Profile (£49). If you have periods, book your test for days 1 to 5 of your cycle; NHS Lothian notes that misleading rises in testosterone can occur later in the cycle. Hormonal contraception raises SHBG and lowers active testosterone, so tell your practitioner if you use it, and do not stop contraception without medical advice.

What blood tests cannot tell you

Blood tests support a PCOS diagnosis but cannot make it alone. You can have PCOS with normal blood tests, for example with irregular periods plus excess hair growth or polycystic ovaries on a scan. Equally, a raised testosterone or AMH does not mean PCOS if your periods are regular and other causes have not been excluded.

The NHS notes that an ultrasound scan of the ovaries is only done in people over 18. Blood tests also cannot assess how PCOS affects your mood: the international guideline recommends screening everyone with PCOS for depression, and adults for anxiety, so mention any low mood or worry to your GP.

When to see a GP urgently

Most PCOS symptoms develop slowly. See a GP promptly if:

• excess hair growth is getting worse quickly, or you notice signs of virilisation such as a deepening voice or increased muscle bulk, which NHS guidance treats as a red flag needing specialist assessment
• a blood test shows testosterone above 5 nmol/L
• you have missed 3 periods in a row, or bleed between periods or after sex
• you feel very thirsty, pee more than usual, feel very tired or lose weight without trying, which can be signs of type 2 diabetes

Call 999 or go to A&E if you have symptoms such as being sick, stomach pain, deep breathing, breath that smells fruity or confusion, as the NHS says these can be signs of diabetic ketoacidosis, even if you have not been diagnosed with diabetes.

Frequently asked questions

Can a blood test diagnose PCOS?

No single blood test can. PCOS is diagnosed when you have 2 of 3 features (irregular ovulation, raised androgens and polycystic ovaries) and other conditions have been ruled out. Blood tests provide evidence for some of these and rule out look-alikes.

Can you have PCOS with normal testosterone?

Yes. Raised androgens can be shown by signs such as excess hair growth instead of a blood test, and some people have PCOS through irregular periods plus polycystic ovaries alone. Checking SHBG and the free androgen index also matters, because low SHBG can mean more active testosterone even when the total is normal.

What day of my cycle should I have PCOS blood tests?

If you are having periods, days 1 to 5 of your cycle are usually advised for hormone tests. If your periods have stopped or are very infrequent, the test can be done on any day.

Does the pill affect PCOS blood tests?

Yes. Oestrogen in combined hormonal contraception raises SHBG and lowers active testosterone, which can hide raised androgens. Tell your practitioner which contraception you use, and get medical advice before stopping it.

PCOS blood tests in Chiswick

Omnia Lifestyle is at 8 to 9 Bedford Corner, The Avenue, Chiswick, London W4 1LZ, a short walk from Turnham Green station (District line; Piccadilly line trains stop there early morning and late evening only) and served by buses 94, E3 and 272. Limited parking is available on request when you book. Every clinic test price includes your sample taken at the clinic, analysis at the Randox accredited laboratory, a practitioner review of your result with you, and a GP feedback report on request. You do not need a GP referral, and most results are back within a few working days.

Useful links: book the Hormone Health Check or the Hormone and Thyroid Panel Plus, browse our women's health blood tests, or compare every blood test and price. Our guides to testosterone levels in women and AMH levels explain these results, and can you get pregnant with PCOS covers fertility. If you would like support alongside your GP care, see our PCOS care at Omnia.

This article is general information, not medical advice. Discuss your results with your GP or practitioner.