PCOS is diagnosed when you meet at least two of three criteria: signs of excess androgens (male-pattern hormones), irregular or absent periods, and polycystic ovaries visible on ultrasound or detected through a blood marker. There is no single test that confirms PCOS on its own. Instead, diagnosis involves a combination of symptom evaluation, blood work, and imaging, along with ruling out other conditions that look similar.
The Three Diagnostic Criteria
The standard framework for diagnosing PCOS, updated most recently in 2023, requires that you meet at least two of the following three criteria:
- High androgen levels: Either visible signs like excess hair growth or acne, or elevated levels on blood tests.
- Ovulatory dysfunction: Irregular, infrequent, or absent periods, which signal that ovulation isn’t happening regularly.
- Polycystic ovaries: A characteristic pattern of many small follicles on ultrasound, or an elevated level of a hormone called anti-Müllerian hormone (AMH) in the blood.
The 2023 international guidelines added AMH as an accepted alternative to ultrasound. This means that if you can’t get an ultrasound or if one isn’t appropriate (as with teenagers), a blood test measuring AMH can serve the same diagnostic purpose. Because only two of the three criteria are needed, you can be diagnosed with PCOS even if your ovaries look completely normal on imaging, as long as you have both excess androgens and irregular cycles.
What “Irregular Periods” Means Clinically
Not every off-cycle counts as ovulatory dysfunction. For a PCOS diagnosis, irregular periods are defined as cycles longer than 35 days apart or fewer than 8 cycles per year. Complete absence of periods also qualifies. If your cycles fall within this range consistently, it suggests your body isn’t ovulating reliably, which is one of the core features of the condition.
How Excess Androgens Are Assessed
Androgens can be evaluated two ways: by looking at your body for physical signs, or by measuring hormone levels in your blood. Often both are done.
The most common physical sign is hirsutism, which is hair growth in areas more typical for men, such as the chin, upper lip, chest, and lower abdomen. Clinicians score this using a standardized system that rates hair growth across several body areas. A score of 8 or higher on this scale is considered clinical hirsutism. Severe acne and thinning hair at the scalp can also count as clinical signs of elevated androgens.
For blood work, total testosterone is the most reliable marker. In PCOS, testosterone levels typically fall at or below 150 ng/dL. If your testosterone comes back above 200 ng/dL, that’s high enough that your provider will want to investigate other causes, including ovarian or adrenal tumors. A hormone called DHEA-S may also be checked. It’s often normal or only slightly elevated in PCOS, but values above 800 µg/dL point toward a potential adrenal tumor rather than PCOS.
What Happens During Ultrasound
A pelvic ultrasound, usually done transvaginally for the clearest image, looks at the size of your ovaries and counts the small fluid-filled sacs (follicles) inside them. Despite the name “polycystic,” these aren’t true cysts. They’re immature follicles that started developing but never released an egg.
The thresholds for what counts as polycystic ovary morphology vary by age. For women under 25, the cutoff is generally 13 follicles per ovary and an ovarian volume of 12 mL or more. Between ages 25 and 29, the threshold shifts to about 14 follicles and a volume of 10 mL. For women in their 30s, the numbers drop further: 10 follicles and a volume of 8 to 9 mL. These age-adjusted thresholds exist because younger women naturally have more follicles, and applying a single standard to everyone would lead to false diagnoses in younger patients.
The Four PCOS Phenotypes
Because only two of three criteria are needed, different combinations produce different presentations of PCOS. Clinicians recognize four phenotypes:
- Phenotype A: All three features present: excess androgens, irregular cycles, and polycystic ovaries. This is sometimes called “full-blown” PCOS.
- Phenotype B: Excess androgens and irregular cycles, but normal-looking ovaries on ultrasound.
- Phenotype C: Excess androgens and polycystic ovaries, but regular ovulation and normal periods.
- Phenotype D: Irregular cycles and polycystic ovaries, but no signs of excess androgens.
Phenotypes A and B, which both involve high androgens and ovulatory problems, tend to carry greater metabolic risks like insulin resistance and cardiovascular concerns. Phenotype D, the non-androgenic type, is generally milder but still benefits from monitoring. Knowing your phenotype can help shape which aspects of management matter most for you.
Conditions That Must Be Ruled Out First
PCOS is partly a diagnosis of exclusion, meaning your provider needs to confirm that your symptoms aren’t caused by something else. Several conditions can mimic PCOS, and standard workup typically includes blood tests to check for thyroid disorders, elevated prolactin levels (which can disrupt cycles and come from a benign pituitary growth), and signs of excess cortisol production, which could indicate Cushing’s syndrome. Late-onset congenital adrenal hyperplasia, a genetic condition that also raises androgen levels, is another common look-alike that’s checked through blood work.
This step is not optional. Skipping it risks missing a treatable condition that requires a completely different approach.
Why Diagnosis Differs for Teenagers
Diagnosing PCOS in adolescents is tricky because many hallmarks of the condition, like irregular periods, acne, and ovaries full of developing follicles, are also normal features of puberty. Ovarian size and follicle counts increase rapidly during adolescence and peak around age 20, making adult ultrasound thresholds unreliable for teens.
Because of this overlap, the diagnostic bar is set higher for adolescents. Both irregular menstrual cycles and clinical or biochemical evidence of excess androgens are required. Ultrasound findings alone aren’t used as a criterion during adolescence. The definition of “irregular” also shifts depending on how far a teenager is from her first period: cycles that would be considered abnormal for an adult may be developmentally normal for someone who started menstruating a year ago.
This stricter approach helps prevent overdiagnosis in teens whose bodies are still maturing, while still catching those who genuinely have the condition early enough to manage long-term health risks.
What the Diagnostic Process Looks Like
In practice, a PCOS evaluation usually starts with a detailed history of your menstrual patterns and any symptoms you’ve noticed, such as new hair growth, persistent acne, or difficulty losing weight. From there, expect a physical exam that includes checking for visible signs of excess androgens and, in some cases, scoring hair growth patterns.
Blood work typically comes next. At minimum, you’ll have testosterone and DHEA-S levels drawn, along with tests to rule out thyroid disease and other mimics. Your provider may also order fasting glucose and insulin levels, since insulin resistance is closely tied to PCOS even though it’s not part of the formal diagnostic criteria. An AMH level may be added, particularly if ultrasound isn’t feasible or preferred.
If ultrasound is done, it’s ideally scheduled during the early part of your cycle (days 2 through 5 after your period starts) for the most accurate follicle count. The entire diagnostic process, from first visit through blood results and imaging, often takes two to four weeks depending on scheduling and how quickly lab results come back. Some people get a clear answer in a single visit if their symptoms and initial blood work are straightforward.