PCOS is diagnosed when you meet at least two of three criteria: irregular or absent ovulation, high androgen levels (either visible on your body or measured in blood), and a specific pattern of follicles on an ovarian ultrasound. There is no single test that confirms it. Instead, diagnosis involves a combination of symptom assessment, blood work, and imaging, along with ruling out other conditions that can look similar.
The Three Diagnostic Criteria
The standard framework for diagnosing PCOS is the Rotterdam criteria, which require any two of the following three features:
- Irregular ovulation: This shows up as missed periods, cycles longer than 35 days, or fewer than eight cycles per year. Some people stop getting periods altogether.
- High androgens: Elevated levels of hormones like testosterone, detected either through blood tests (biochemical hyperandrogenism) or through visible signs like excess hair growth, acne, or hair thinning (clinical hyperandrogenism).
- Polycystic ovarian morphology: A characteristic appearance on ultrasound showing a high number of small follicles in the ovaries or enlarged ovarian volume.
You don’t need all three. Two of three is enough for a diagnosis, which means someone with irregular periods and high testosterone but normal-looking ovaries on ultrasound still qualifies. This also means the name “polycystic ovary syndrome” is a bit misleading: you can have PCOS without polycystic-appearing ovaries, and the “cysts” aren’t true cysts but small fluid-filled follicles.
What Happens During the Physical Exam
Your doctor will look for visible signs of excess androgens. The most structured way to assess excess hair growth is the Ferriman-Gallwey scoring system, which rates hair density on 11 body areas (lip, chin, chest, upper and lower abdomen, upper arms, forearms, thighs, lower legs, upper and lower back) on a scale of 0 to 4 each. A total score of 8 or higher out of a possible 36 is considered diagnostic of hirsutism. Your doctor will also check for hormonal acne, thinning hair on the scalp, and a skin change called acanthosis nigricans, which appears as dark, velvety patches on the neck, armpits, or groin and signals insulin resistance.
Blood Tests You Can Expect
Blood work serves two purposes: confirming high androgens and ruling out other conditions. For androgen levels, total testosterone is typically preferred over free testosterone because the lab assays are more reliable. Most testosterone values in PCOS fall at or below 150 ng/dL. Values at or above 200 ng/dL raise concern for an androgen-secreting tumor in the ovaries or adrenal glands and require further workup. Your doctor may also check DHEA-S, an adrenal androgen. Mildly elevated levels are common in PCOS, but values at or above 800 µg/dL suggest a possible adrenal tumor.
Timing matters for accurate results. If your doctor needs to confirm that you’re not ovulating, progesterone should be drawn during the midluteal phase of your cycle, roughly a week before your expected period. If you’re on hormonal birth control, androgen levels will be artificially suppressed. Guidelines recommend stopping hormonal contraceptives for at least three months before testing for biochemical hyperandrogenism, since the hormones increase sex hormone binding globulin, which lowers the amount of active testosterone in your blood.
Conditions That Must Be Ruled Out
PCOS is a diagnosis of exclusion, meaning your doctor has to make sure nothing else is causing your symptoms before confirming it. The list of conditions that can mimic PCOS is longer than most people expect:
- Thyroid dysfunction: Both an overactive and underactive thyroid can disrupt your cycle. A simple TSH blood test screens for this.
- High prolactin: Markedly elevated prolactin can signal a pituitary tumor and cause missed periods.
- Non-classic congenital adrenal hyperplasia: This genetic condition causes the adrenal glands to overproduce androgens. A blood test measuring 17-hydroxyprogesterone can identify it.
- Cushing syndrome: Excess cortisol production can cause weight gain, irregular periods, and acne.
- Pregnancy: A simple hCG test rules this out.
- Primary ovarian insufficiency: High FSH and LH with low estradiol, or undetectable AMH in someone under 40, points to premature loss of ovarian function rather than PCOS.
Your doctor may not order every one of these tests. Which ones are needed depends on your specific symptoms and how you present.
What the Ultrasound Looks For
A transvaginal ultrasound checks the number of follicles in each ovary and the overall ovarian volume. The thresholds for what counts as polycystic morphology vary by age. In women under 25, the cutoff is roughly 13 follicles per ovary and an ovarian volume of about 12 to 13 mL. For women in their early 30s, the thresholds drop to around 10 follicles and 9 mL. By the early 40s, 9 follicles and 10 mL are the benchmarks. These age-adjusted cutoffs exist because younger women naturally have more follicles, so applying a single number across all ages would lead to overdiagnosis in younger patients.
A 2023 update to the international PCOS guidelines introduced an alternative to ultrasound: a blood test measuring anti-Müllerian hormone (AMH). AMH is produced by the small follicles in your ovaries, so elevated levels can serve as a stand-in for the follicle count you’d see on imaging. This can be useful when a transvaginal ultrasound isn’t available or preferred. However, AMH should not be used as a standalone test for PCOS. It only replaces the ultrasound component. If you already have irregular cycles and confirmed hyperandrogenism, you meet two criteria and don’t need AMH or ultrasound at all.
How Diagnosis Differs for Teenagers
Diagnosing PCOS in adolescents requires extra caution. Irregular periods are normal in the first few years after a teenager’s first period, and many healthy adolescents have ovaries that look polycystic on ultrasound simply because their reproductive system is still maturing. For these reasons, current guidelines recommend against using ovarian ultrasound as a diagnostic criterion in teenagers. This effectively rules out the standard Rotterdam criteria for this age group.
Instead, a PCOS diagnosis in an adolescent generally requires both irregular cycles (beyond what’s expected for their stage of development) and clear evidence of hyperandrogenism, either through blood tests or persistent clinical signs like significant hirsutism or severe acne that doesn’t respond to typical treatments. If there’s uncertainty, some clinicians will label the situation “at risk for PCOS” and reassess a few years later rather than making a definitive diagnosis too early. AMH testing is also not recommended for adolescents at this time.
Metabolic Screening at Diagnosis
Once PCOS is confirmed, most guidelines recommend screening for metabolic complications, since the condition increases your risk of insulin resistance, type 2 diabetes, and cardiovascular disease regardless of your weight. This typically includes a fasting glucose or oral glucose tolerance test, a lipid panel, and blood pressure measurement. These aren’t part of the PCOS diagnosis itself, but they’re a standard part of the workup because catching metabolic problems early changes how your condition is managed.
Insulin resistance affects an estimated 50 to 70 percent of people with PCOS, even those at a normal weight. If your metabolic screening comes back normal, it’s generally repeated every one to three years depending on your risk factors.