Blood Tests for PCOS: The Complete Hormone Guide
Polycystic ovary syndrome affects 1 in 10 Australian women. The right blood tests are essential for diagnosis, excluding mimics, assessing metabolic risk, and monitoring treatment — yet many women wait years for a proper workup.
What Is PCOS and Why Are Blood Tests Important?
Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of reproductive age, affecting approximately 8–13% of women worldwide and an estimated 1.2 million Australian women. Despite the name, PCOS is primarily a hormonal and metabolic condition — not all women have “cysts” on their ovaries, and many women with polycystic-appearing ovaries on ultrasound do not have PCOS.
Diagnosis uses the Rotterdam criteria (2003, updated 2023): at least 2 of 3 features must be present — (1) irregular or absent periods (oligo-anovulation), (2) clinical signs of excess androgens (acne, hirsutism, hair loss) OR elevated androgens on blood tests (biochemical hyperandrogenism), and (3) polycystic ovarian morphology on ultrasound or elevated AMH. Crucially, other conditions that mimic PCOS must be excluded first.
Blood tests serve multiple purposes in PCOS: confirming biochemical hyperandrogenism, excluding thyroid disease and other mimics, assessing insulin resistance and metabolic risk (which is elevated in PCOS regardless of weight), screening for cardiovascular risk factors, and monitoring treatment response over time.
5 Key Blood Test Groups for PCOS
Androgen Panel
What these tests measure: Androgens are the hallmark hormones of PCOS. Elevated androgens cause the characteristic symptoms — acne, excess facial and body hair (hirsutism), scalp hair thinning, and oily skin. Total testosterone is the most commonly measured, but free testosterone (the biologically active fraction) is more sensitive for detecting mild hyperandrogenism. SHBG (sex hormone-binding globulin) is often low in PCOS, which increases the proportion of free testosterone even when total testosterone is normal.
How to interpret: Total testosterone above 2.0 nmol/L or free testosterone above 30 pmol/L suggests hyperandrogenism. Low SHBG (below 30 nmol/L) amplifies androgen effects. DHEA-S is primarily adrenal — if elevated alone (above 10 µmol/L), consider adrenal causes (congenital adrenal hyperplasia, adrenal tumour). Androstenedione above 10 nmol/L supports PCOS but is not routinely measured.
Australian context: The RCPA recommends measuring total testosterone and SHBG as first-line for suspected PCOS. Free testosterone can be calculated from total testosterone and SHBG using the Vermeulen equation (some labs report this automatically). Androgen testing should ideally be done in the early follicular phase (days 1–7) of the menstrual cycle for consistency, and in the morning when testosterone peaks.
LH/FSH Ratio
What these tests measure: In PCOS, the pituitary gland often produces excess LH relative to FSH, disrupting normal ovulation. The classic finding is an LH:FSH ratio greater than 2:1 or 3:1. Elevated LH stimulates the ovarian theca cells to produce more androgens, while relatively low FSH impairs follicle development, leading to the characteristic “string of pearls” appearance on ultrasound (multiple small follicles that fail to mature).
How to interpret: LH:FSH ratio above 2:1 is suggestive of PCOS, but this is NOT required for diagnosis — approximately 40% of women with PCOS have a normal ratio. A ratio below 1:1 may suggest other causes of anovulation (hypothalamic amenorrhoea, premature ovarian insufficiency). FSH should be in the normal range for PCOS — elevated FSH (above 25 IU/L) suggests diminished ovarian reserve.
Australian context: The 2023 International Evidence-based Guideline for PCOS (endorsed by the Jean Hailes Foundation and Australian endocrinology societies) no longer requires the LH/FSH ratio for diagnosis. However, many Australian GPs and gynaecologists still order it as supportive evidence. It is bulk billed under Medicare when ordered with an appropriate clinical indication.
Insulin Resistance Testing
What these tests measure: Insulin resistance is present in 50–80% of women with PCOS, regardless of weight. It is a key driver of the condition — high insulin levels stimulate the ovaries to produce excess androgens and suppress SHBG production. Fasting insulin is the most practical screening test, though it has limitations (high variability between labs). HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) is calculated from fasting insulin and glucose and provides a standardised score.
How to interpret: Fasting insulin above 10–12 mU/L suggests insulin resistance. HOMA-IR above 2.0 is the commonly used threshold, though some experts use 2.5 for Australian populations. HbA1c is useful for screening for prediabetes/diabetes (above 6.0% warrants attention) but does NOT measure insulin resistance directly. A 2-hour OGTT is the gold standard for detecting impaired glucose tolerance.
Australian context: Fasting insulin is NOT bulk billed on its own under Medicare — it requires an additional clinical indication such as suspected PCOS, acanthosis nigricans, or impaired fasting glucose. HbA1c and fasting glucose are bulk billed. The 2023 International PCOS Guideline recommends all women with PCOS have a baseline OGTT or HbA1c, repeated every 1–3 years depending on risk factors.
Conditions to Rule Out
What these tests measure: Before diagnosing PCOS, your GP or endocrinologist must exclude conditions that mimic it. Thyroid disorders (both hyper and hypothyroidism) can cause irregular periods and weight changes. Elevated prolactin (from a pituitary adenoma or medication) causes anovulation. Non-classic congenital adrenal hyperplasia (NCAH) is particularly important to exclude — it affects up to 5% of women presenting with apparent PCOS and requires different treatment.
How to interpret: TSH should be in the normal range (0.5–4.0 mIU/L). Prolactin above 1000 mIU/L warrants further investigation. 17-hydroxyprogesterone (17-OHP) is the key screening test for NCAH — a fasting, early-morning level above 6 nmol/L requires an ACTH stimulation test. If 17-OHP is above 30 nmol/L after stimulation, NCAH is confirmed.
Australian context: Australian endocrinology guidelines require TSH and prolactin in every PCOS workup. 17-OHP screening is recommended for all women with hyperandrogenism, particularly those of Mediterranean, Middle Eastern, Hispanic, or Ashkenazi Jewish ancestry where NCAH carrier rates are higher. All exclusion tests are bulk billed under Medicare.
Fertility & AMH Testing
What these tests measure: AMH (anti-Müllerian hormone) is produced by the granulosa cells of small ovarian follicles. In PCOS, AMH is typically elevated — often 2–4 times the normal range — reflecting the high number of small, arrested follicles. While AMH is not yet formally included in the Rotterdam diagnostic criteria, the 2023 international guideline now recognises elevated AMH as an alternative to ultrasound for confirming polycystic ovarian morphology in adults.
How to interpret: AMH above 35 pmol/L (or 5.0 ng/mL) in women under 35 is strongly suggestive of PCOS. Day 21 progesterone below 16 nmol/L confirms anovulation (the cycle in question). If progesterone is above 16 nmol/L, ovulation occurred that cycle, which does not exclude PCOS (some women with PCOS ovulate intermittently).
Australian context: AMH testing is bulk billed in Australia when ordered for investigation of infertility or suspected PCOS. Day 21 progesterone is bulk billed for ovulation confirmation. Fertility assessment in PCOS should include partner semen analysis and tubal assessment before assuming PCOS is the sole cause of subfertility. Monash University’s Jean Hailes Foundation provides free evidence-based PCOS resources for Australian patients.
When to Get Blood Tests: Timing Matters
Hormone levels fluctuate throughout the menstrual cycle, so timing affects accuracy:
Androgens (testosterone, SHBG, DHEA-S): Days 1–7 of cycle (early follicular phase), fasting, morning
LH and FSH: Days 2–5 of cycle for baseline ratio
Progesterone: Day 21 (or 7 days before expected period) to confirm ovulation
Fasting insulin and glucose: Morning, after 10–12 hour fast
Prolactin: Morning, fasting, avoid stress (stress raises prolactin)
AMH: Can be drawn any time in the cycle (not cycle-dependent)
What to Ask Your GP
Script for your GP appointment:
“I've been experiencing irregular periods / acne / excess hair growth / difficulty losing weight and I'd like to be investigated for PCOS. Could we check my testosterone, SHBG, LH/FSH, fasting insulin, thyroid function, and 17-hydroxyprogesterone? I'd also like a metabolic screen including fasting glucose and lipids.”
| Test | Purpose | Cost (Australia) |
|---|---|---|
| Total Testosterone + SHBG | Detect hyperandrogenism (core diagnostic criterion) | Bulk billed |
| LH + FSH | Assess gonadotropin ratio and exclude other causes | Bulk billed |
| DHEA-S | Screen for adrenal androgen excess | Bulk billed |
| TSH | Exclude thyroid disorders | Bulk billed |
| Prolactin | Exclude hyperprolactinaemia | Bulk billed |
| 17-Hydroxyprogesterone | Screen for congenital adrenal hyperplasia | Bulk billed |
| Fasting Glucose + HbA1c | Screen for insulin resistance / diabetes | Bulk billed |
| Fasting Insulin | Quantify insulin resistance (HOMA-IR) | Bulk billed* |
| AMH | Ovarian follicle assessment (alternative to ultrasound) | Bulk billed* |
| Lipid Profile | Cardiovascular risk screening (common in PCOS) | Bulk billed |
* Fasting insulin and AMH are bulk billed when ordered with appropriate clinical indication (suspected PCOS, infertility investigation). Some labs may not bulk bill fasting insulin without a glucose result.
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Reference ranges sourced from the Royal College of Pathologists of Australasia (RCPA) and the 2023 International Evidence-based Guideline for the Assessment and Management of PCOS. SmarterBlood provides health information and AI-powered blood test analysis. It is not a substitute for professional medical advice, diagnosis, or treatment.