PCOS Blood Tests: The Labs Worth Asking About
Labs · Testing · Updated 2026-07-31
There is no single blood test for PCOS. Diagnosis follows the Rotterdam criteria, which require two of three features - clinical or biochemical hyperandrogenism, ovulatory dysfunction, and polycystic ovarian morphology - after other conditions have been excluded. Blood work does two jobs in that process: it measures androgens, and it rules out the thyroid disease, high prolactin, non-classic congenital adrenal hyperplasia and other causes that can imitate PCOS.
The panel that follows is what commonly appears in PCOS evaluation and follow-up, with the reference ranges usually printed alongside each result. The one most often missing from a routine draw is fasting insulin, and it is the one worth asking for by name. Your clinician decides what fits your case; this list exists to make that conversation sharper, not to replace it.
The diagnostic panel: androgens and exclusions
| Lab | Typical adult female reference | What it is for |
|---|---|---|
| Total testosterone | About 15 to 70 ng/dL (0.5 to 2.4 nmol/L) | The headline androgen. Values well above range prompt a search for other causes |
| Free testosterone or calculated free T | Roughly 0.1 to 6.4 pg/mL by assay | The unbound, active fraction. Often the more sensitive marker in PCOS |
| SHBG | About 20 to 130 nmol/L | Binds testosterone. Low SHBG raises free testosterone and is strongly linked to insulin resistance |
| Free Androgen Index | Calculated: total T (nmol/L) / SHBG (nmol/L) x 100 | Used when free testosterone is not measured directly; commonly flagged above about 5 |
| DHEA-S | About 35 to 430 ug/dL, falling with age | The adrenal androgen. Shows whether excess androgen is ovarian, adrenal or both |
| 17-hydroxyprogesterone | Below about 200 ng/dL, drawn fasting in the morning | Screens for non-classic congenital adrenal hyperplasia, a PCOS mimic |
| TSH | About 0.4 to 4.0 mIU/L | Thyroid disease disrupts cycles and must be excluded |
| Prolactin | About 4 to 23 ng/mL | High prolactin is another common cause of missed periods |
Two practical notes on this panel. Androgens are usually drawn in the morning, when levels peak, and combined hormonal contraception suppresses many of them - so results taken on the pill often cannot be interpreted, and a washout period may be needed before testing. The 2023 international evidence-based PCOS guideline also recommends using a high-quality assay such as liquid chromatography-mass spectrometry for testosterone where available, because direct immunoassays perform poorly at the low concentrations typical in women.
The metabolic panel: what is often left off
| Lab | Reference | What it catches |
|---|---|---|
| Fasting insulin | Roughly 2 to 20 uIU/mL by assay | Rises years before glucose does. Rarely on a routine panel unless requested |
| Fasting glucose | 70 to 99 mg/dL | 100 to 125 mg/dL is prediabetes |
| HOMA-IR | Calculated: insulin x glucose / 405 (mg/dL) or / 22.5 (mmol/L) | Below 1.9 usually sensitive, 2.5 and above commonly flags resistance |
| HbA1c | Below 5.7 percent | Three-month glucose average. Often normal early in insulin resistance |
| 75 g oral glucose tolerance test | 2-hour value below 140 mg/dL | The most sensitive of the glucose tests; often preferred when risk is higher |
| Lipid panel | Triglycerides below 150 mg/dL, HDL above 50 mg/dL | PCOS is associated with higher cardiometabolic risk, so lipids get checked |
| AMH | Assay dependent; often elevated in PCOS | Reflects small follicle count. See the AMH guide for how it is read |
Timing, units and the mistakes that waste a draw
- Fast for insulin, glucose and lipids - usually 8 to 12 hours, water only, unless your clinician says otherwise.
- Draw androgens in the morning, ideally in the early follicular phase if you are cycling, since that is where most reference ranges were established.
- Flag hormonal contraception before the draw. The pill lowers androgens and raises SHBG, which can mask the very pattern being investigated.
- Copy down the units. A testosterone in ng/dL and one in nmol/L differ by a factor of about 28.8, and comparing across labs without noting units is how people frighten themselves unnecessarily.
- Keep every report, not just abnormal ones. A value inside range that has moved steadily across three years is often more informative than a single flagged result.
One record instead of five portals. PCOS Diet & Symptom Tracker by Panda Taps keeps testosterone, SHBG, DHEA-S, fasting insulin and glucose, HbA1c, AMH, thyroid and the rest in one place with their units and reference ranges, next to your logged symptoms, meals and cycles. When labs scatter across clinics and portals the trend disappears - keeping them together is how you bring better data to your appointments. Download PCOS Diet & Symptom Tracker on the App Store.
How often labs get repeated
Diagnostic labs are usually run once, unless something is equivocal. Metabolic follow-up is ongoing: the 2023 international PCOS guideline recommends assessing glycaemic status at diagnosis and then every one to three years depending on individual risk factors, and checking a lipid profile at diagnosis with subsequent frequency based on that result and overall cardiovascular risk. Blood pressure is recommended yearly. In practice, many care teams also recheck a few key labs three to six months after a meaningful treatment change, to see whether it did what it was supposed to.
A tracked lab history changes the shape of an appointment. Instead of one result read in isolation, your clinician sees direction, and direction is what decisions are actually made on. Pair this with a prepared appointment plan and the HOMA-IR guide. Educational content only - testing and interpretation belong with your clinician.
Frequently asked questions
What blood test confirms PCOS?
None on its own. PCOS is diagnosed from the Rotterdam criteria, needing two of three features - androgen excess, ovulatory dysfunction and polycystic ovarian morphology - with thyroid disease, high prolactin and non-classic congenital adrenal hyperplasia excluded first. Blood work supports that process rather than settling it.
Should I fast before PCOS blood work?
For insulin, glucose and lipids, yes - usually 8 to 12 hours with water only. Androgens do not strictly require fasting but are typically drawn in the morning. Follow the instructions your lab or clinician gives you.
Can I get accurate PCOS labs while on the pill?
Often not. Combined hormonal contraception suppresses androgens and raises SHBG, which can hide the biochemical picture. Many clinicians ask for a washout period of around three months before testing androgens. Never stop a prescribed medication without discussing it first.
How often should PCOS labs be repeated?
The 2023 international guideline suggests glycaemic assessment every one to three years by risk, lipids at diagnosis with follow-up guided by the result, and blood pressure annually. Many clinicians also recheck key labs a few months after a treatment change.