The PCOS Blood Test Panel: What Each Number Means

You have a printed lab sheet or a portal full of asterisks, and someone wrote "consistent with PCOS" without explaining which numbers led there. This post walks each test in the panel, when it should have been drawn, what counts as borderline, and what got missed if anything did.

What is FSH on a blood test? Follicle-stimulating hormone (FSH) is a pituitary hormone that signals the ovary to recruit and grow follicles in the first half of each cycle. It is one of the core hormones on the PCOS panel, alongside luteinising hormone (LH), oestradiol, testosterone, sex hormone-binding globulin (SHBG), DHEAS, anti-Mullerian hormone (AMH), prolactin, thyroid-stimulating hormone (TSH), and 17-hydroxyprogesterone (17-OHP). The 2023 international PCOS guideline lays out which of these are needed, when they should be drawn, and how the values should be interpreted.¹ This post is the patient-facing version of that same framework.

If you want the diagnostic logic that these labs feed into, the pillar post is How PCOS Is Diagnosed: The Rotterdam Criteria Explained.

Why the timing of the draw matters

Most of the hormones on the PCOS panel are not stable across the cycle. The same FSH can read as 4 on day 3 and 8 on day 10. The same testosterone can read normal in the morning and high mid-afternoon. Getting the timing right is half the test.

• FSH, LH, oestradiol, and 17-OHP are early-follicular tests. Ideally cycle days 2 to 5. If you are anovulatory and there is no obvious cycle to time off, they can be drawn on any day, but the report needs to note that the cycle phase was unknown.
• Mid-luteal progesterone is the simplest test of whether ovulation actually happened. Draw it 7 days before the expected next period. For a 28-day cycle that is day 21; for a 35-day cycle that is day 28.
• Testosterone is best measured in the morning, in the follicular phase, after at least three months off hormonal contraception. Combined oral contraceptives suppress androgens and make biochemical hyperandrogenism uninterpretable.¹
• Prolactin is a morning, fasted, non-stressed draw. Recent exercise, a breast exam earlier in the appointment, or even a stressful commute can falsely raise it. If a single value comes back mildly elevated, the protocol is to repeat under proper conditions before doing anything else.
• AMH is the exception. It is cycle-phase independent and stable across the cycle.³ You can draw it any day, on or off the pill (though COCP lowers AMH slightly), and the value is comparable.

If your lab sheet does not state the cycle day or has the wrong day for the test, the interpretation is shaky and may need a repeat draw. This is the single most common reason a panel is "normal" but the clinical picture says otherwise.

The hormones that build the PCOS picture

LH, FSH, and the LH:FSH ratio

In the follicular phase, FSH normally runs between roughly 3 and 10 IU/L, and LH between roughly 2 and 10 IU/L. The classic PCOS pattern is an LH:FSH ratio above 2, often quoted as the "2-to-1" pattern. The 2023 international guideline removed the LH:FSH ratio as a diagnostic criterion because about 30 to 40 percent of people with PCOS have a normal ratio, and using the ratio alone over- and under-calls the diagnosis in different groups.¹

A high FSH (above 10 to 15 IU/L on cycle day 3) points away from PCOS and toward diminished ovarian reserve. That is a different conversation and needs its own follow-up. See AMH, FSH, and LH Explained. Very low FSH and LH with low oestradiol points toward hypothalamic amenorrhoea, which mimics PCOS on the cycle history but has the opposite hormonal pattern.

So what is the FSH and LH blood test useful for in PCOS? It is useful for ruling out ovarian insufficiency and hypothalamic amenorrhoea. It is not useful as a stand-alone diagnostic test for PCOS.

Androgens: total and free testosterone, SHBG, DHEAS, androstenedione

This is the bucket where the most measurement error happens. Standard immunoassays for testosterone perform poorly at the low concentrations seen in women, and the Endocrine Society position statement is explicit that borderline values should be confirmed with mass spectrometry.²

• Total testosterone above roughly 2.5 nmol/L (about 70 ng/dL) suggests biochemical hyperandrogenism. The exact cutoff is lab-dependent.
• SHBG is the protein that binds testosterone in the blood. It is often low in PCOS because insulin lowers SHBG production by the liver. Low SHBG raises the free, biologically active fraction of testosterone, which is why someone can have a normal total T and still be symptomatic.
• Free androgen index (FAI) = (total T × 100) / SHBG. A more sensitive marker of androgen excess in the PCOS pattern.
• DHEAS reflects adrenal androgen contribution. A modest elevation is common in PCOS. A markedly elevated DHEAS prompts a 17-OHP and an adrenal workup.
• Androstenedione is sometimes added when DHEAS is borderline or when the picture is unclear.

The single value to flag urgently: total testosterone above 5 nmol/L (150 ng/dL), particularly if the symptoms came on suddenly or include virilising features. That is not routine PCOS and needs an androgen-secreting tumour workup, not a slow lab repeat.

AMH: anti-Mullerian hormone

AMH is produced by the granulosa cells of small antral and pre-antral follicles, and the value reflects the size of that follicle pool.³ In PCOS, the pool is large, so AMH is often elevated. As a rough orientation, AMH above 35 pmol/L (5 ng/mL) is commonly elevated in PCOS, but every lab uses its own assay-specific cutoff, and the number on your report needs to be interpreted against that, not against a round number from the internet.

The 2023 guideline now accepts an elevated AMH as an alternative to ultrasound for the polycystic ovarian morphology criterion in adults, when high-resolution imaging is not available.¹ That is a real change from earlier guidelines and is one of the most useful additions for readers who have had only a transabdominal scan or an older transvaginal probe.

Two things AMH does not do. It does not predict natural conception in this context, because it is a marker of how many follicles are in the pool, not of egg quality. And a high AMH on its own is not a diagnosis; Rotterdam still requires two of three features.¹

The hormones that rule out PCOS mimics

These are the tests that protect you from getting the PCOS label when something else is the actual driver.

• TSH: preconception target is roughly 0.5 to 2.5 mIU/L. A mildly elevated TSH (3 to 5 mIU/L) gets repeated with free T4 and TPO antibodies before treatment. Hypothyroidism imitates PCOS through oligomenorrhoea and weight gain. See Thyroid, TSH, and Fertility.
• Prolactin: drawn fasted in the morning. A mildly elevated single value (under about 1000 mIU/L, or under about 50 ng/mL) is often stress or assay variation; repeat fasted before acting on it. A persistently elevated prolactin needs pituitary imaging.¹ See Prolactin and Fertility.
• 17-hydroxyprogesterone: early morning, follicular phase. A value above 6 nmol/L (2 ng/mL) prompts an ACTH stimulation test to exclude non-classic congenital adrenal hyperplasia, a 21-hydroxylase deficiency that closely mimics PCOS.⁴
• Cortisol screening: only done if Cushing's syndrome features are present (purple striae, central obesity disproportionate to BMI, easy bruising, proximal muscle weakness). Not routine.

If any of these come back abnormal, the diagnosis shifts and the management plan changes. Most clinicians order them as part of the first-visit panel; if yours did not, ask why.

Metabolic numbers your clinician should also draw

The 2023 guideline is firm that metabolic screening is part of the PCOS workup, regardless of BMI.¹ The Endocrine Society clinical practice guideline from 2013 was the first to frame this clearly, and the 2023 update endorsed it.⁵

• Fasting glucose and HbA1c
• A 2-hour oral glucose tolerance test (OGTT), recommended in all adults with PCOS regardless of BMI. Fasting glucose alone misses early insulin resistance and impaired glucose tolerance.
• A fasting lipid panel. PCOS is associated with elevated triglycerides and low HDL, sometimes with normal LDL.
• Blood pressure and waist circumference

Fasting insulin is not recommended as a diagnostic test. HOMA-IR (a derived insulin-resistance index) is too imprecise outside research settings to drive clinical decisions.¹ If your lab includes either, treat them as background information, not as the deciding number.

Numbers that look concerning but often are not

• LH above FSH on a random draw in someone with irregular cycles. Common, not diagnostic by itself.
• Slightly elevated prolactin (under 1000 mIU/L, under 50 ng/mL). Often stress or assay variation. Repeat fasted before acting.
• Mildly elevated TSH (3 to 5 mIU/L). Repeat with free T4 and TPO antibodies before treating.
• Borderline total testosterone. Always repeat with SHBG and free androgen index, and confirm with mass spectrometry if the value falls in the grey zone.

I see all four of these flagged as "abnormal" on patient portals, sometimes with red asterisks, and they panic people. None of them is, on its own, an emergency.

Numbers that need a same-week call to your clinician

• Total testosterone above 5 nmol/L (150 ng/dL), particularly with sudden-onset symptoms or virilising features. Needs androgen-secreting tumour workup.
• DHEAS very high. Same logic.
• TSH above 10 mIU/L. Overt hypothyroidism. Start replacement before conception attempts continue.
• Prolactin above 1000 mIU/L (50 ng/mL) on a confirmed repeat. Needs pituitary imaging.
• Fasting glucose at or above 7 mmol/L (126 mg/dL), or HbA1c at or above 6.5 percent. That is a diabetes diagnosis, and it changes preconception care significantly.

Most PCOS panels do not turn up any of these. But the ones that do should not wait for the next routine appointment.

What to do this week with your report

Three concrete steps when you get your lab sheet back:

1. Annotate every test with the cycle day it was drawn. If a test that needs follicular timing was drawn at the wrong phase, flag it for a repeat.
2. Cross-check the panel against the list in this post. If any of TSH, prolactin, or 17-OHP are missing, ask for them. The Rotterdam criteria cannot be applied until the mimics are ruled out.¹
3. Ask your clinician explicitly which Rotterdam features your labs support. If the conversation stays at "your numbers are consistent with PCOS," push for the specifics. Which feature, measured how, against what threshold.

What's next

• For the imaging side of the workup, read PCOS on Ultrasound: What Doctors Actually See.
• For the diagnostic framework these numbers feed into, the pillar is How PCOS Is Diagnosed: The Rotterdam Criteria Explained.
• If AMH is the deciding feature in your case, read AMH, FSH, and LH Explained.
• If you suspect lean PCOS and want to know how the panel reads at normal BMI, read Lean PCOS: When You Don't Match the Stereotype.
• If your thyroid or prolactin was flagged, the dedicated posts are Thyroid, TSH, and Fertility and Prolactin and Fertility.

Sources

1. Teede HJ, Tay CT, Laven JJE, Dokras A, Moran LJ, Piltonen TT, et al. Recommendations from the 2023 International Evidence-Based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Fertility and Sterility 2023;120(4):767–793. https://doi.org/10.1016/j.fertnstert.2023.07.025
2. Rosner W, Auchus RJ, Azziz R, Sluss PM, Raff H. Position statement: Utility, limitations, and pitfalls in measuring testosterone: an Endocrine Society position statement. Journal of Clinical Endocrinology & Metabolism 2007;92(2):405–413. https://doi.org/10.1210/jc.2006-1864
3. Dewailly D, Andersen CY, Balen A, Broekmans F, Dilaver N, Fanchin R, et al. The physiology and clinical utility of anti-Müllerian hormone in women. Human Reproduction Update 2014;20(3):370–385. https://doi.org/10.1093/humupd/dmt062
4. Speiser PW, Arlt W, Auchus RJ, Baskin LS, Conway GS, Merke DP, et al. Congenital Adrenal Hyperplasia Due to Steroid 21-Hydroxylase Deficiency: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism 2018;103(11):4043–4088. https://doi.org/10.1210/jc.2018-01865
5. Legro RS, Arslanian SA, Ehrmann DA, Hoeger KM, Murad MH, Pasquali R, Welt CK. Diagnosis and treatment of polycystic ovary syndrome: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology & Metabolism 2013;98(12):4565–4592. https://doi.org/10.1210/jc.2013-2350