Testing for PCOS involves a combination of blood work, a physical exam, and sometimes an ultrasound. There’s no single test that confirms or rules it out. Instead, doctors look for at least two of three key features: elevated male-type hormones, irregular or absent ovulation, and polycystic-appearing ovaries. Just as importantly, they need to rule out other conditions that can mimic PCOS before making a formal diagnosis.
The Three Criteria Doctors Look For
PCOS is diagnosed using what’s known as the Rotterdam criteria, which require at least two of the following three features:
- High androgen levels. Either measured in your blood or visible as symptoms like excess facial and body hair, acne, or thinning hair on your scalp.
- Ovulatory dysfunction. Irregular periods, very long cycles (over 35 days), or missing periods entirely.
- Polycystic ovaries. Detected on ultrasound or through elevated levels of a hormone called anti-Müllerian hormone (AMH).
You don’t need all three. Two out of three is enough for a diagnosis, provided other conditions have been excluded. This means some people with PCOS have perfectly regular-looking ovaries on ultrasound, and others have normal androgen levels but meet the other two criteria.
Blood Tests Your Doctor Will Order
Hormone blood work is the backbone of PCOS testing. The most commonly measured hormones include total and free testosterone, DHEA-S (an androgen produced by the adrenal glands), androstenedione, LH, FSH, prolactin, and progesterone. Each reveals something different about what’s happening hormonally.
The numbers that raise suspicion for PCOS: a total testosterone above 40 ng/dL, a DHEA-S level above 200 ug/dL, or an LH level that’s two to three times higher than FSH. In healthy women, LH and FSH levels are roughly equal, so a significant imbalance is a red flag.
Free testosterone is especially useful because it measures the testosterone actually active in your body, not the portion bound to proteins and essentially inactive. Normal free testosterone ranges from 0.7 to 3.6 pg/mL.
Timing matters for these tests. Blood should be drawn early in the morning after fasting. If you have regular periods, the best window is between days 5 and 9 of your menstrual cycle (counting the first day of your period as day 1). If your periods are irregular or absent, your doctor may draw blood at any time or use medication to induce a period first.
Ruling Out Other Conditions
Before a PCOS diagnosis can be made, your doctor needs to exclude other conditions that cause similar symptoms. Thyroid disorders can cause irregular periods and hair changes. High prolactin levels (from a benign pituitary gland issue) can disrupt ovulation. Adrenal gland disorders can spike androgen levels in ways that look identical to PCOS from the outside.
This is why the blood panel typically includes thyroid hormones and prolactin alongside the androgen tests. If your androgen levels are extremely high or you’re showing signs of rapid masculinization (like a deepening voice), your doctor may also test for ovarian or adrenal tumors, though these are rare.
The Physical Exam
A clinical assessment of excess hair growth uses a scoring system called the Ferriman-Gallwey scale, which rates hair density across several body areas including the upper lip, chin, chest, back, and abdomen. A score of 8 or higher meets the threshold for clinical hyperandrogenism, meaning your symptoms alone can satisfy one of the three diagnostic criteria without needing a blood test to confirm elevated androgens.
Your doctor will also look for acne patterns (particularly along the jawline and chin), thinning hair at the crown, and a darkening of skin in the folds of the neck, groin, or underarms, which can signal insulin resistance.
Ultrasound and Ovarian Assessment
A transvaginal ultrasound can check for polycystic ovarian morphology. The current threshold is 20 or more follicles per ovary when using a high-resolution ultrasound transducer, or 12 or more with older equipment. These follicles are small, fluid-filled sacs, not cysts in the traditional sense, and they’re a sign that multiple eggs began developing but none matured enough to ovulate.
Ovarian volume of 10 mL or above has also been used as a marker, but recent research shows it has weaker diagnostic value than follicle count. In a study of over 2,200 women with PCOS, only 0.6% would have been missed if ovarian volume were dropped from the criteria entirely. Follicle count declines naturally after age 35, so ultrasound becomes less reliable for older women.
An alternative to ultrasound is measuring AMH through a blood test. AMH is produced by the small follicles in your ovaries, so elevated levels reflect the same ovarian picture an ultrasound would show. This option is especially useful when a transvaginal ultrasound isn’t practical or preferred.
Metabolic Testing for Insulin Resistance
PCOS testing doesn’t stop at the diagnosis. Because insulin resistance affects a large proportion of people with PCOS regardless of body weight, screening for blood sugar problems is strongly recommended.
The gold standard here is an oral glucose tolerance test (OGTT), where you drink a sugary solution and have your blood sugar measured two hours later. This is significantly more accurate than a fasting blood sugar alone. Research from a tertiary care center found that relying only on fasting glucose missed 40% of women with blood sugar abnormalities, including every case of diabetes in the study group. A fasting glucose level can look perfectly normal while your body is already struggling to process sugar after meals.
Your doctor may also check fasting insulin levels, a lipid panel (cholesterol and triglycerides), and hemoglobin A1C, which reflects your average blood sugar over the past two to three months. These tests help build a fuller picture of your metabolic health and guide treatment decisions.
Testing in Teenagers
Diagnosing PCOS in adolescents is tricky because many hallmark features of PCOS, like irregular periods, acne, and even mildly elevated androgens, are normal during puberty. The American College of Obstetricians and Gynecologists advises caution in assigning a PCOS diagnosis to anyone within two years of their first period.
Pelvic ultrasound is generally not helpful in this age group. Polycystic ovarian morphology shows up in 30 to 40% of adolescent girls and is not predictive of whether they will develop PCOS. Instead, the most reliable diagnostic clue in teens is a free or total testosterone level above normal adult female values, combined with persistent menstrual irregularity well beyond the first couple of years after menarche. If a teenager’s symptoms are concerning but don’t clearly meet the criteria, doctors will often monitor over time rather than label the condition prematurely.
What to Expect at Your Appointment
If you suspect PCOS and want to get tested, start with your primary care doctor or a gynecologist. Bring a record of your menstrual cycles for the past several months, including cycle length and flow. Mention any symptoms you’ve noticed: new or worsening facial hair, persistent acne, unexplained weight changes, or difficulty getting pregnant.
Most of the blood work can be done in a single morning visit if timed correctly in your cycle. Results typically come back within a few days. An ultrasound, if needed, is usually scheduled separately. From first appointment to diagnosis, the process often takes a few weeks, depending on how quickly you can get labs and imaging done. If your results are borderline, your doctor may repeat certain tests or refer you to an endocrinologist or reproductive specialist for further evaluation.