PCOS diagnosis in Australia: the criteria, the blood tests and what the results show.
PCOS is diagnosed by a doctor using two of three features: irregular or absent ovulation, signs of high androgens, and polycystic ovaries on ultrasound (or a raised AMH in adults). There is no single PCOS blood test. Blood results feed into one or two of those criteria and rule out look-alike conditions. Here is how the pieces fit.
The Rotterdam criteria in plain English
Polycystic ovary syndrome (PCOS) affects roughly 10 to 13 per cent of women of reproductive age, and many are not diagnosed for years. The international guideline, led from Australia and updated in 2023, uses what are still called the Rotterdam criteria. An adult meets them when she has two of the following three features, and other causes have been ruled out:
- Irregular or absent ovulation. In practice, cycles consistently shorter than 21 days or longer than 35, fewer than about eight periods a year, or periods that have stopped.
- Signs of high androgens (male-type hormones). Either on a blood test, as a raised testosterone or free androgen index, or clinically, as excess facial or body hair, persistent acne, or thinning hair on the scalp.
- Polycystic ovaries on ultrasound, or a raised AMH. "Polycystic" means many small follicles, not cysts in the everyday sense. In adults, a raised AMH can now be used instead of the scan.
Two features are enough. A woman with regular periods can meet the criteria (high androgens plus polycystic ovaries), and so can a woman with a normal scan (irregular cycles plus high androgens). The rules are stricter in teenagers: within eight years of a first period, both irregular cycles and high androgens are needed, and ultrasound is not used because many normal adolescent ovaries look polycystic.
Why is there no single PCOS blood test?
Because PCOS is a pattern, not a single measurement. No one hormone is raised in every woman with the condition. Around a quarter of women who meet the criteria have testosterone in the normal range, and many women with a slightly raised testosterone do not have PCOS. The LH to FSH ratio is a supporting clue, not a requirement.
Blood tests do three things well: show whether androgens are raised (criterion two), stand in for the ultrasound in adults via AMH (criterion three), and rule out conditions that mimic PCOS. The first criterion, irregular ovulation, comes from your cycle history. A doctor puts the sources together. A panel on its own cannot.
The blood tests used and what each shows
These are the markers usually on a PCOS request form, and the job each one does.
| Marker | What it checks | What it usually means |
|---|---|---|
| Total testosterone | The main circulating androgen | Raised in many, but not all, women with PCOS; very high levels prompt a search for other causes |
| SHBG | The carrier protein that binds testosterone | Often low in PCOS, especially with insulin resistance; low SHBG means more free testosterone |
| Free androgen index | A calculation from testosterone and SHBG | A better guide to active androgen than testosterone alone; raised values support criterion two |
| DHEA-S | An androgen made mainly by the adrenal glands | Mildly raised in some women with PCOS; markedly raised levels point towards the adrenals instead |
| LH and FSH | The pituitary signals that drive the ovaries | LH often runs higher than FSH in PCOS; a normal ratio does not rule it out |
| Prolactin | Rules out raised prolactin as the cause | Usually normal in PCOS; a mild rise is often stress or timing and is repeated |
| TSH | Rules out thyroid disease as the cause | About 0.4 to 4.0 mIU/L is typical; outside that, thyroid is investigated first |
| AMH | Reflects the number of small follicles | Often raised in PCOS; accepted in adults in place of ultrasound, with the cut-off set by the assay |
| Fasting glucose | Blood sugar after an overnight fast | Read with HbA1c as the glycaemic pair the guideline recommends. Fasting insulin and HOMA-IR are not recommended for assessing an individual, because the assay is not standardised between laboratories, so they are not in the KnowLuna panel |
| HbA1c | Three-month average blood sugar | 6.5% or above is in the diabetes range; 6.0 to 6.4% is the at-risk zone doctors watch |
| Lipid profile | Cholesterol and triglycerides | Sets a baseline for long-term heart health, which PCOS affects |
Ranges vary by laboratory; your report shows the range your lab uses. Typical ranges on this page are drawn from Pathology Tests Explained (RCPA) and the sources listed below.
Androgens are best measured off hormonal contraception, because the combined pill raises SHBG and lowers testosterone; the guideline suggests at least three months off before testing, where that is safe and practical. Insulin and lipids need a fasting sample, so the panel is collected in the morning after eight to twelve hours with water only.
Free androgen index explained, with the formula
The free androgen index (FAI) answers one question: of the testosterone in your blood, how much is free to act on tissues? Most testosterone travels bound to SHBG, where it is inactive. When SHBG is low, a larger share is free. Measuring free testosterone directly is difficult in women, so laboratories calculate an index instead.
That is why two women with identical testosterone can have very different symptoms. Most Australian laboratories report a normal FAI for women as below about 5 to 7, depending on the laboratory. A raised FAI counts towards criterion two even when total testosterone is normal. Because SHBG falls with insulin resistance and rises on the pill, your doctor reads the FAI in that context.
Ultrasound: when it is and is not needed
A transvaginal ultrasound is the traditional way to assess the third criterion. The current definition counts 20 or more small follicles in at least one ovary, or an ovarian volume of 10 mL or more, on a modern transvaginal scan, with no corpus luteum, cyst or dominant follicle present. Where an older machine or an abdominal scan is used, a follicle count of 10 or more per section or the same ovarian volume is used instead. It is useful, but often not needed:
- Not needed when two criteria are already met. Irregular cycles plus raised androgens stand without a scan.
- Not used in adolescents. Within eight years of a first period, polycystic-looking ovaries are common and normal.
- Can be replaced by AMH in adults. Since 2023 a raised AMH can substitute for the scan when one other criterion is present. AMH is not used in teenagers either.
- Still useful when the picture is unclear, when AMH is borderline, or when the doctor wants to look at the uterus and ovaries for other reasons.
If a scan is suggested, your doctor arranges it through a standard imaging referral. KnowLuna does not perform ultrasound.
Insulin resistance and PCOS: why metabolic markers are in the panel
The name points at the ovaries, but PCOS is as much a metabolic condition as a reproductive one. Most women with PCOS have some degree of insulin resistance: the body needs more insulin than usual to keep blood sugar normal. That extra insulin pushes the ovaries to make more androgens and lowers SHBG, which raises the free androgen index. It occurs at every body size, so it cannot be assumed from weight.
This is why fasting glucose, HbA1c and lipids sit next to the hormones. They do not make the diagnosis, but they describe your metabolic starting point, and the guideline recommends checking blood sugar and cardiovascular risk at diagnosis and then every one to three years depending on your risk, because women with PCOS have a higher long-term risk of type 2 diabetes. Fasting insulin and HOMA-IR are imperfect, poorly standardised measures that the guideline recommends against for an individual assessment; the test it names as most accurate for blood sugar is a 75 g oral glucose tolerance test, with fasting glucose or HbA1c as alternatives, arranged through your doctor. Our article on insulin resistance testing in women explains the numbers.
Your KnowLuna PCOS panel result
The KnowLuna PCOS panel covers the blood-test side of the criteria in one fasting morning collection: testosterone, SHBG, free androgen index, LH, FSH, prolactin, TSH, DHEA-S, fasting glucose, HbA1c and lipids. The plain-English report groups them as androgens, cycle signals, rule-outs and metabolic markers, so you can see which criteria your results speak to.
What the report will not do is tell you that you have PCOS. That decision belongs with a doctor who also has your cycle history and, if needed, a scan or AMH. With the doctor-requested option, a KnowLuna women's health doctor talks the results through in a 20-minute video consult and outlines next steps. Companion articles cover what a PCOS blood test can and can't show and what to expect on the day. If weight and insulin are your main questions, see the weight and metabolic check.
Common questions
What are the main signs of PCOS?
Doctors look for irregular or infrequent periods, excess facial or body hair, persistent acne along the jaw and chin, thinning scalp hair, and difficulty conceiving. Weight gain around the middle and dark velvety skin patches can point to insulin resistance. Many women have only one or two of these, and none is specific to PCOS on its own.
What are the three markers for PCOS?
The three diagnostic criteria are irregular ovulation, high androgens (on blood tests or as symptoms) and polycystic ovaries on ultrasound or a raised AMH. Two of three are needed. The blood androgen markers are total testosterone, SHBG and the free androgen index, with DHEA-S as a supporting measure.
What blood tests are done for PCOS?
A typical panel includes testosterone, SHBG and the free androgen index for androgens; LH, FSH and sometimes AMH for the ovaries; prolactin and TSH to rule out other causes; and fasting glucose, HbA1c and lipids for the metabolic side. Fasting is needed for the metabolic markers, and androgens are best measured off hormonal contraception.
Can I have PCOS with normal blood tests?
Yes. Around a quarter of women who meet the criteria have normal testosterone, and the LH to FSH ratio is often normal. With irregular cycles plus either clinical signs of high androgens (hair, acne) or polycystic ovaries on ultrasound, a doctor can still make the diagnosis. Normal bloods narrow the picture; they do not close it.
Do I need an ultrasound to be diagnosed with PCOS?
Not always. If two criteria are already met from your cycle history and androgen results, no scan is needed. In adults, a raised AMH can stand in for the ultrasound. Ultrasound is not used within eight years of a first period, because polycystic-looking ovaries are common in teenagers.
Can people with PCOS get pregnant?
Many do, naturally and with help. PCOS can make ovulation less frequent, which reduces the chances each year, but it does not mean infertility. If you are trying to conceive with irregular cycles, a doctor can check whether ovulation is happening and talk through options. A timed progesterone test is one simple way to confirm ovulation.
Sources and further reading
- Monash University: International Evidence-based Guideline for the Assessment and Management of PCOS 2023
- Teede HJ et al. Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of PCOS. J Clin Endocrinol Metab 2023
- Jean Hailes: International PCOS Guideline 2023 and resources
- Pathology Tests Explained (RCPA): testosterone
- Pathology Tests Explained (RCPA): anti-Mullerian hormone (AMH)
- Healthdirect: polycystic ovarian syndrome (PCOS)
General information only, not medical advice. If your symptoms are severe or sudden, see a doctor promptly. This page does not replace a consultation with a doctor who knows your history; read our medical disclaimer.
PCOS and your hormones: what a blood test can and can't show
Why PCOS is a clinical diagnosis, and where the panel fits in.
Irregular, late or missing periods: which blood tests your doctor checks
The common causes and the tests that sort them out.
Insulin resistance testing in women
Fasting glucose, HbA1c and what the numbers mean.