How Is PCOS Diagnosed? Tests, Criteria and What to Expect

PCOS (polycystic ovary syndrome) affects roughly 1 in 10 women of childbearing age, yet many go years without a clear answer. Doctors diagnose it when you have at least two of three features: irregular or absent ovulation, signs of higher androgen levels, and polycystic ovaries on ultrasound or a high AMH level. Before confirming it, they also rule out other conditions that can look similar, such as thyroid problems or high prolactin.

If you've been living with unpredictable periods, stubborn acne or unwanted hair growth, you might already suspect PCOS. Getting a diagnosis can feel like piecing together a puzzle, but once you know what doctors look for, the process becomes much less mysterious. Here's how it works, step by step.

Why there's no single PCOS test

PCOS doesn't look the same in everyone. One woman may skip periods for months but have clear skin. Another may have regular-looking cycles but higher testosterone and thinning hair. Many signs also overlap with other conditions, or with normal changes in the teenage years.

So instead of one test, doctors put together several pieces: your cycle history, a physical exam, blood work and sometimes an ultrasound. For a broader overview of the condition, read our guide to PCOS signs and causes.

The three criteria doctors use

Most doctors use the Rotterdam criteria, which current international guidelines are built on. You need at least two of these three:

1. Irregular or absent ovulation. Cycles longer than 35 days, fewer than eight periods a year, or periods so unpredictable you can't plan around them.
2. Signs of higher androgens. Androgens are hormones such as testosterone. Higher levels can show up as acne, extra hair on the face, chest or belly, or thinning hair on the scalp. They can also be measured in a blood test.
3. Polycystic ovaries or a high AMH level. On ultrasound, the ovaries may show many small follicles, sometimes lined up around the edge like a string of pearls. In adults, guidelines now allow a blood test for AMH (anti-Müllerian hormone) to be used instead.

Having only one of these doesn't mean you have PCOS. Small follicles on an ultrasound are also common in women without the condition.

Other definitions you may hear about

You might come across other sets of criteria, too. The older NIH definition requires both irregular ovulation and high androgens. The Androgen Excess and PCOS Society definition requires high androgens plus one of the other two features. These stricter versions can lead to a slightly different answer, which is one reason it helps to ask your doctor exactly which features you meet.

What happens at your appointment

• Your health history. Expect questions about your periods, weight changes, skin and hair, family history and medications.
• A physical exam. Your doctor may check your blood pressure, weight and signs such as acne, hair growth or darker, velvety skin patches.
• Blood tests. These measure hormones and rule out other causes.
• An ultrasound, if needed. A pelvic or transvaginal scan shows the number of follicles and the size of your ovaries.

Common blood tests and what they look for

• Testosterone and other androgens, often with SHBG, a protein that affects how much testosterone is active
• Thyroid hormone (TSH), because thyroid problems can cause irregular periods
• Prolactin, since high levels can stop ovulation
• 17-hydroxyprogesterone, to rule out a rare adrenal condition with similar signs
• A pregnancy test, to rule out pregnancy as the reason for missed periods
• AMH, in some cases, as part of the diagnosis

Because PCOS is linked to insulin resistance, your doctor may also check blood sugar and cholesterol. These don't diagnose PCOS, but they help guide long-term care.

A note for teenagers

Irregular cycles and acne are very common in the first few years after periods begin. That's why guidelines advise against using ultrasound to diagnose PCOS within eight years of a first period. Teens may be described as "at risk" and checked again later.

What to track before your visit

A little preparation can save you time and a second appointment:

• Write down your period dates for at least the past three months.
• Note skin and hair changes, such as acne flare-ups or new hair growth.
• Record any weight changes and how your energy has been.
• List your medications and supplements.
• Ask whether you need to fast before blood tests, or test on a certain cycle day.

If you're trying to conceive, say so. It shapes which tests your doctor orders, and it's a good moment to plan a check-up for your partner, too.

Questions worth asking your doctor

• Which criteria do I meet, and how certain is the diagnosis?
• Do my results suggest anything else that should be checked?
• Should I be screened for blood sugar or cholesterol, and how often?
• How might PCOS affect my plans to get pregnant?
• Which lifestyle changes would help me most?

After a diagnosis

A PCOS diagnosis can feel overwhelming at first, but it also brings clarity and a plan. For many women with extra weight, losing even 5 to 10 percent of body weight can help periods become more regular. Balanced meals with plenty of vegetables, whole grains and lean protein, plus regular movement you enjoy, are the foundation. Our article on PCOS treatment options explains what doctors may recommend.

Supporting your body along the way

Alongside your doctor's advice, balanced meals, regular movement, good sleep and stress care form the foundation of PCOS self-care. Some women also choose targeted nutrition. AGO Mom supports stable hormones and menstrual regulation, supports reproductive health, and helps reduce the risk of infertility related to PCOS. Paired with AGO Women, which is formulated to help support hormonal balance, a regular cycle and overall vitality, it can be part of a broader care routine alongside medical guidance.