PCOS is diagnosed when you meet at least two of three criteria: signs of elevated androgens (male hormones), irregular or absent ovulation, and polycystic-appearing ovaries on ultrasound. There is no single test that confirms it. Instead, diagnosis involves a combination of blood work, a physical assessment, and sometimes imaging, along with tests that rule out other conditions that look similar.
The Three Diagnostic Criteria
The standard framework used worldwide is the Rotterdam criteria, endorsed by the Endocrine Society and updated most recently in 2023 international guidelines. You need two of these three to qualify for a PCOS diagnosis:
- Hyperandrogenism: Either clinical signs like excess hair growth and acne, or elevated androgen levels on blood work, or both.
- Ovulatory dysfunction: Irregular periods, very long cycles, or absent periods, indicating you aren’t ovulating regularly.
- Polycystic ovaries: A specific pattern on ultrasound, or an elevated AMH blood level (more on both below).
If you already have both irregular cycles and clear signs of high androgens, you don’t need an ultrasound or AMH test at all. Those two criteria alone are enough. Importantly, your doctor also needs to rule out other conditions that can cause the same symptoms before confirming PCOS.
What Counts as Irregular Periods
Ovulatory dysfunction doesn’t just mean your period is a few days late sometimes. In the context of PCOS, it typically means cycles longer than 35 days, fewer than eight cycles per year, or no period at all for three or more months. Your age matters here too. The 2023 international guidelines note that in adolescents (within the first eight years after a first period), some cycle irregularity is normal, so the diagnostic bar is set higher for younger patients. In teens, both hyperandrogenism and ovulatory dysfunction must be present; ultrasound and AMH are not recommended because they aren’t reliable at that age.
Blood Tests for Androgen Levels
The core blood work checks whether your body is producing too many androgens. The hormones typically measured include total testosterone, free testosterone, and DHEA-S (an androgen made by the adrenal glands). A total testosterone level above roughly 40 ng/dL, a DHEA-S level above 200 µg/dL, or a ratio where your LH level is two to three times higher than your FSH level all raise suspicion for PCOS.
Normal reference ranges are broad. Total testosterone in women generally falls between 6 and 86 ng/dL, free testosterone between 0.7 and 3.6 pg/mL, and DHEA-S between 35 and 430 µg/dL. Where you fall within those ranges, combined with your symptoms, is what matters. A level that’s technically “in range” but sitting at the high end can still be clinically significant if you also have acne, hair loss, or excess body hair.
Timing Your Blood Draw
Hormone levels fluctuate throughout your cycle, so timing matters. Androgens and other baseline hormones like LH, FSH, and 17-hydroxyprogesterone are best measured during the follicular phase (roughly days 2 through 5 of your cycle). If your doctor wants to confirm whether you’re ovulating, progesterone is typically drawn around day 22 to 23. If your periods are very irregular or absent, your doctor may draw blood at any point since there’s no reliable cycle day to target.
Physical Signs Your Doctor Will Assess
Excess hair growth in androgen-sensitive areas, called hirsutism, is one of the most common visible signs of PCOS. Doctors evaluate this using a scoring system called the modified Ferriman-Gallwey scale, which rates hair growth across nine body areas: upper lip, chin, chest, upper and lower back, upper and lower abdomen, upper arms, and thighs. Each area gets a score from 0 (no excess hair) to 4 (extensive growth), and the numbers are added up.
A total score of 8 or higher is the standard threshold for hirsutism, but this was established in predominantly white populations. The cutoff varies significantly by ethnicity. For East Asian women, thresholds as low as 2 to 6 have been proposed depending on the specific population studied. Your doctor should consider your ethnic background when interpreting hair growth patterns. Beyond hirsutism, acne along the jawline and chin, thinning hair on the scalp, and skin darkening in the folds of the neck or underarms (a sign of insulin resistance) are all physical findings that factor into a PCOS evaluation.
Ultrasound and AMH Testing
A pelvic ultrasound looks at the structure of your ovaries. The diagnostic threshold is 12 or more small follicles (each 2 to 9 mm in diameter) in an ovary, or an ovarian volume of 10 mL or greater. Newer guidelines using higher-resolution ultrasound equipment have raised the follicle count threshold to 25 or more per ovary, since modern machines detect more follicles than older ones did.
A transvaginal ultrasound (where the probe is inserted vaginally rather than placed on your abdomen) gives a much clearer picture and is the preferred approach in adults. It’s painless for most people, though it can feel uncomfortable. The name “polycystic” is somewhat misleading. The follicles seen on ultrasound aren’t true cysts. They’re small, fluid-filled sacs containing immature eggs that haven’t been released during ovulation.
As an alternative to ultrasound, the 2023 guidelines now formally recognize AMH (anti-Müllerian hormone) as a blood test that can substitute for imaging. AMH reflects the number of small follicles in your ovaries. A level at or above 3.8 ng/mL has been estimated to be over 80% accurate for identifying polycystic ovarian morphology. This is especially useful for adolescents or anyone who prefers to avoid a transvaginal ultrasound.
Tests That Rule Out Other Conditions
Several other conditions mimic PCOS symptoms, and your doctor needs to exclude them before making a diagnosis. This is a standard part of the workup, not an optional extra. The key tests include:
- Thyroid function (TSH): An underactive or overactive thyroid can cause irregular periods and hair changes that look like PCOS.
- Prolactin level: Elevated prolactin (a hormone involved in milk production) can stop ovulation and cause missed periods. A small percentage of people with PCOS do have mildly elevated prolactin, but very high levels point to a different diagnosis.
- 17-hydroxyprogesterone: This test screens for non-classic congenital adrenal hyperplasia, a genetic condition affecting the adrenal glands that causes excess androgen production. It’s measured during the follicular phase. A level below 1,000 ng/dL after a stimulation test effectively rules it out.
In more severe cases, particularly if you have complete absence of periods or signs of rapid masculinization (deepening voice, significant muscle bulk), your doctor may also evaluate for Cushing’s disease, adrenal or ovarian tumors, or conditions affecting the pituitary gland.
Metabolic Screening After Diagnosis
Once PCOS is confirmed, most doctors will also screen for insulin resistance and related metabolic issues, since these affect a large percentage of people with the condition regardless of body weight. The most commonly used test is a two-hour glucose tolerance test, where you drink a sugary solution and have blood drawn at intervals to measure both glucose and insulin. About 45% of reproductive endocrinologists use this as their primary screening tool. Others rely on fasting insulin and glucose levels, or a fasting glucose-to-insulin ratio.
This metabolic screening isn’t part of the PCOS diagnosis itself, but it shapes your treatment plan. Insulin resistance drives many PCOS symptoms, and identifying it early gives you more options for managing both the hormonal and metabolic sides of the condition. Your doctor will typically also check cholesterol levels and blood pressure as part of this broader assessment.
What to Bring to Your Appointment
Tracking your menstrual cycles for at least three months before your appointment gives your doctor concrete data to work with. Note the start date of each period, how long it lasts, and any gaps longer than 35 days. If you’ve noticed new or worsening acne, hair growth in unusual places, or hair thinning on your scalp, document when these changes started. Photos taken over time can be helpful. If you’ve had blood work or ultrasounds done previously, bring those results. Having this information ready can speed up the diagnostic process and reduce the number of follow-up visits you need.