There is no single test that confirms PCOS. Instead, diagnosis relies on a combination of blood work, a review of your menstrual history, a physical exam, and sometimes an ultrasound or hormone level check. Most doctors use what’s known as the Rotterdam criteria, which require at least two of three features: signs of excess androgens (male-type hormones), irregular or absent ovulation, and a specific appearance of the ovaries on imaging. Before a diagnosis is made, other conditions that look similar to PCOS need to be ruled out.
The Three Diagnostic Criteria
The international standard for diagnosing PCOS in adults asks whether you meet at least two of three criteria. The first is hyperandrogenism, meaning your body is producing or responding to higher-than-typical levels of androgens. This can show up as visible symptoms (excess hair growth, acne, hair thinning) or as elevated hormone levels on a blood test. The second is ovulatory dysfunction: cycles that are consistently irregular, very long, or absent altogether. A normal cycle falls roughly between 21 and 35 days; cycles regularly outside that range, or fewer than eight cycles per year, point to a problem with ovulation. The third is polycystic ovarian morphology, where an ultrasound shows a high number of small follicles on one or both ovaries, or the ovaries are enlarged.
You don’t need all three. Two out of three is enough, as long as other explanations have been excluded. This means some people with PCOS have perfectly regular-looking ovaries on ultrasound, while others ovulate normally but have clear signs of androgen excess. PCOS looks different from person to person, which is part of why diagnosis can feel confusing.
Blood Tests Your Doctor May Order
Blood work plays two roles in a PCOS workup: checking for elevated androgens and ruling out other conditions. The most commonly measured hormone is total testosterone. In PCOS, testosterone levels are often mildly elevated but typically stay at or below 150 ng/dL. Values above 200 ng/dL raise concern for something more serious, like an ovarian or adrenal tumor, and prompt further investigation. Your doctor may also check a hormone called DHEA-S, which comes from the adrenal glands. It can be normal or slightly elevated in PCOS, but levels at or above 800 µg/dL suggest the possibility of an adrenal tumor.
It’s worth knowing that testosterone values can be completely normal in PCOS. A normal blood test doesn’t rule it out if you have clinical signs of androgen excess (like significant excess hair growth) and irregular cycles.
To exclude conditions that mimic PCOS, doctors typically test thyroid function and prolactin levels. They also check a marker called 17-hydroxyprogesterone to rule out a form of congenital adrenal hyperplasia, a genetic condition that causes similar symptoms. These “rule out” tests are a standard part of the process.
The Physical Exam
A physical exam can establish androgen excess without any blood work at all. Doctors use a standardized scoring system that evaluates terminal (coarse, dark) hair growth across 11 body areas: the lip, chin, chest, upper and lower abdomen, upper arm, forearm, thigh, lower leg, upper back, and lower back. Each area is scored from 0 (no excess hair) to 4 (extensive growth). A total score of 8 or higher out of a possible 36 is considered diagnostic of hirsutism, the medical term for excess hair growth driven by androgens. Severe acne and thinning hair at the crown can also count as clinical signs of hyperandrogenism.
Ultrasound and AMH Testing
Pelvic ultrasound has long been used to look for polycystic ovarian morphology, where the ovaries contain a high number of small, fluid-filled follicles arranged around the outer edge. Updated 2023 international guidelines now recognize an alternative: a blood test measuring anti-Müllerian hormone (AMH). AMH is produced by the small follicles in the ovaries, so elevated levels can serve as a proxy for what an ultrasound would show.
The guidelines specifically recommend using either ultrasound or AMH to assess ovarian morphology, but not both. Using both tests together increases the chance of overdiagnosis. For many people, this means the diagnosis can be made with blood work and a clinical assessment alone, without ever needing an ultrasound.
How Diagnosis Differs for Teenagers
Diagnosing PCOS in adolescents is trickier because the features of PCOS overlap with normal puberty. Irregular cycles are common in the first few years after a first period, and many healthy teenagers have ovaries that look polycystic on ultrasound without having the condition. For this reason, current guidelines recommend against using pelvic ultrasound as a diagnostic tool in adolescents. Instead, diagnosis in teenagers requires both irregular menstrual cycles (evaluated relative to how many years it’s been since their first period) and clear evidence of hyperandrogenism, either from blood tests or clinical signs. If there’s uncertainty, doctors may assign an “at risk” label and reassess over time rather than giving a definitive diagnosis too early.
Metabolic Screening After Diagnosis
Once PCOS is confirmed, your doctor will likely screen for metabolic complications, particularly insulin resistance and glucose intolerance. Up to 70% of people with PCOS have some degree of insulin resistance, meaning their cells don’t respond efficiently to insulin, which can lead to higher blood sugar over time. An oral glucose tolerance test, where you drink a sugary solution and have your blood drawn at intervals, is considered the best simple office-based method for assessing both insulin resistance and glucose intolerance in PCOS. Fasting glucose, fasting insulin, and HbA1c (a measure of average blood sugar over three months) are also commonly used. Lipid panels and blood pressure checks round out the metabolic picture, since PCOS raises the long-term risk for type 2 diabetes and cardiovascular issues.
What the Process Looks Like in Practice
A typical PCOS evaluation involves one or two appointments. At the first visit, your doctor will ask detailed questions about your cycle length and regularity, look for visible signs of androgen excess, and order blood work. You may be asked to return for an ultrasound or AMH test if needed, though many diagnoses are made without imaging. The entire process usually takes a few weeks, mostly spent waiting for lab results.
If you’re on hormonal birth control, the process gets more complicated. Birth control masks both irregular cycles and androgen levels, so your doctor may ask you to stop it for a few months before testing, or they may rely more heavily on ultrasound or AMH. This is something to discuss before your appointment so you know what to expect.