How PCOS Is Diagnosed: Criteria, Labs, and the AMH Test

Many women with PCOS hear some version of the same thing: "Your ultrasound was normal, so it's not PCOS." Or the reverse: "You have cysts, so it's PCOS," with no other testing.

Neither is how PCOS is actually diagnosed. Here's how it works under the current international guideline, which labs matter, and what needs to be ruled out.

A quick note on the name. In May 2026, PCOS was renamed polyendocrine metabolic ovarian syndrome (PMOS). The diagnostic criteria haven't changed with the name. For the reasons behind the change, see PCOS Symptoms and Root Causes.

The criteria

In adults, PCOS is diagnosed when you have two of these three, after other causes are ruled out:

Irregular cycles or no ovulation. In adults, that generally means cycles shorter than 21 or longer than 35 days, or fewer than eight periods a year.
High androgens, seen either in symptoms (acne, excess hair growth, scalp hair thinning) or on blood tests.
Polycystic ovarian morphology, seen on ultrasound, or now, a high AMH level.

So a woman with irregular cycles and high testosterone has PCOS even if her ovaries look completely normal. And a woman with "polycystic" ovaries but regular cycles and normal androgens doesn't.

The 2023 guideline notes that irregular cycles plus high androgens together capture at least 70% of cases. When you have both, no ultrasound or AMH is needed.

What changed in 2023: AMH can replace the ultrasound

AMH (anti-Müllerian hormone) is made by the small follicles in the ovary. Women with PCOS have more of those follicles, so AMH tends to run high.

The 2023 guideline says adults can use an AMH blood test instead of a pelvic ultrasound for the third criterion. A few rules come with it:

It's either AMH or ultrasound, not both. Using both leads to overdiagnosis.
AMH is never diagnostic on its own. It's one of the three criteria, and only needed if you meet just one of the other two.
Neither test is used within eight years of your first period. In teens and young women, follicle counts and AMH are naturally high, so they can't separate PCOS from normal.

If ultrasound is used, the threshold in adults is 20 or more follicles in at least one ovary, on a modern transvaginal scan.

The labs to ask for

Androgens

Total and free testosterone. These are the core tests. The guideline recommends labs use a method called LC-MS/MS, because standard direct testosterone tests are often inaccurate at the low levels women have. If your result came back normal on a basic test and you have symptoms, it may be worth repeating at a lab that uses LC-MS/MS.
SHBG, so free testosterone or the free androgen index can be calculated.
DHEA-S and androstenedione, which can be considered if testosterone is normal. DHEA-S points more toward the adrenal glands.

A note on timing: if you're on a birth control pill, it lowers androgens and can hide PCOS on labs. The guideline suggests a break of at least three months before testing, with other contraception in the meantime.

Tests to rule out look-alikes

PCOS is a diagnosis of exclusion. Before calling it PCOS, the guideline recommends checking:

TSH, because thyroid problems cause irregular cycles
Prolactin, because high prolactin stops ovulation
17-hydroxyprogesterone, to rule out non-classic congenital adrenal hyperplasia, an inherited adrenal condition that looks very much like PCOS

Very high androgens, or symptoms that appear suddenly or progress quickly, need investigation for other causes, including rare androgen-producing tumors.

For more on other conditions that cause irregular cycles, see Irregular Periods in Your 20s and 30s.

Metabolic tests

This is the part most often skipped. Because insulin resistance is a core feature of PCOS, the guideline recommends checking blood sugar status in every woman with PCOS, at any weight.

A 75 g oral glucose tolerance test (OGTT) is the most accurate test. You drink a glucose solution and blood sugar is checked before and after.
Fasting glucose and HbA1c are the fallback if an OGTT isn't possible, but they miss more cases.
A lipid panel to check cholesterol and triglycerides.
Blood pressure at least yearly.

You'll notice fasting insulin isn't on the guideline's list. The guideline says standard insulin tests aren't reliable enough for routine diagnosis. Many functional medicine doctors still find fasting insulin, alongside glucose, useful for seeing the pattern and tracking progress over time. Just know it isn't used to diagnose PCOS.

Mental health

The guideline recommends screening every woman with PCOS for depression and anxiety, and considering disordered eating at any weight. These are part of the condition, not separate from it.

Your checklist

If you suspect PCOS, these are worth bringing up with your clinician:

A few months of cycle tracking: start dates and cycle length
Total and free testosterone (ideally by LC-MS/MS), SHBG, DHEA-S
TSH, prolactin, and 17-hydroxyprogesterone
AMH or a transvaginal ultrasound, if you only meet one of the first two criteria
A 75 g oral glucose tolerance test, and a lipid panel
A pregnancy test if your period is late

A diagnosis is the starting point, not the plan. Once you know it's PCOS, the work is on insulin, inflammation, and stress, which is where symptoms actually change. Normal labs that don't match how you feel are a separate problem. See "Your Labs Are Normal" for what to do about that.

References

Teede HJ, et al. International evidence-based guideline for the assessment and management of polycystic ovary syndrome 2023: summary of recommendations. Monash University. View source
New evidence-based guideline for PCOS explained (interview with Prof. Helena Teede). Healthed. View source
Endocrine Society. Polyendocrine Metabolic Ovarian Syndrome: new name to improve diagnosis and care. May 12, 2026. View source
Klein DA, Paradise SL, Reeder RM. Amenorrhea: a systematic approach to diagnosis and management. Am Fam Physician. 2019;100(1):39-48. View source