PCOS Diagnosis: How PCOS Is Diagnosed

The three Rotterdam criteria in detail

PCOS affects approximately 10 to 13 percent of women of reproductive age, i.e. about one in eight (WHO, 2025), making it the most common hormonal disorder in this life phase. The diagnosis is based on three possible characteristics, at least two of which must be present. Each individual characteristic alone does not prove anything; only the combination provides a coherent picture.

The first criterion is menstrual cycle irregularities, i.e. rare, irregular or absent ovulation (oligo- or anovulation). In practice, this often means very long or very short cycles, bleeding that stops for months, or a cycle that never really settles down. If you want to know what could be behind absent bleeding, you can find out more in our article Missed period: causes and what helps.

The second criterion is hyperandrogenism, an excess of male hormones. It counts clinically (visible in symptoms such as acne, increased body hair in the sense of hirsutism, or hair loss on the head) or biochemically, i.e. measured in the blood. Both are valid, and often both occur together. We go into more detail on how to recognise and classify elevated androgens in Naturally lowering testosterone in PCOS.

The third criterion is polycystic ovarian morphology, i.e. many small follicles or enlarged ovaries on ultrasound. New since the 2023 international guideline: in adult women, an elevated AMH level can fulfil this criterion instead of ultrasound. And if a cycle disturbance and hyperandrogenism are already present, ultrasound or AMH are no longer strictly necessary for diagnosis.

Incidentally, the name is misleading: the many follicles are not real cysts, and not every woman with PCOS has them. Strictly speaking, the term "polycystic ovary syndrome" is therefore imprecise; the syndrome is more than an ultrasound finding.

Which hormone markers are checked in PCOS?

There is no single PCOS test. Instead, a panel is checked that fulfils two tasks: classifying the androgen status and, at the same time, ruling out other causes. The following overview shows which markers are typically measured and what they tell us.

• Total and free testosterone, free androgen index: the most important marker of hyperandrogenism, reflecting androgen status.
• DHEAS and androstenedione: further androgens that provide clues to the adrenal gland as a possible source.
• LH and FSH: the LH/FSH ratio used to be considered an indicator, but is no longer diagnostically decisive today.
• AMH (Anti-Müllerian hormone): a marker for the number of follicles, which can replace ultrasound in adults.
• TSH, prolactin and 17-OH progesterone: used to rule out thyroid issues, prolactin excess and adrenal hyperplasia.
• Fasting glucose, oGTT and HbA1c: clarify possible insulin resistance and blood sugar.

The timing matters: if you are bleeding, hormones are ideally taken early in the cycle, usually between day 2 and 5. If you are taking the pill, it changes many of these values, which is why it is often discontinued several weeks beforehand for a clean work-up. A single elevated or normal value never decides on its own; the doctor always reads the markers in context with your symptoms.

Ultrasound and AMH: what the images show

Transvaginal ultrasound makes many small follicles and an enlarged ovarian volume visible. Since 2023, a higher threshold than before applies with modern technology.

Specifically, the international guideline refers to polycystic ovarian morphology from around 20 follicles per ovary (with a high-resolution probe of at least 8 MHz) or an ovarian volume of around 10 millilitres. The German S2k guideline of 2025 also specifies the threshold of more than 20 follicles per ovary with a size of 2 to 9 millimetres. The higher number prevents healthy ovaries from being falsely classified as polycystic.

However, an abnormal ultrasound alone is not a diagnosis: many small follicles also occur in completely healthy women. Conversely, a normal ultrasound does not rule out PCOS if the other criteria are met. This is precisely why the AMH level is interesting as an alternative, because it correlates closely with the follicle count. In a meta-analysis on diagnostic accuracy, AMH in adult women achieved a sensitivity of around 79 percent and a specificity of around 87 percent (van der Ham et al., 2024). However, it is not a quick test to be evaluated in isolation, but only one component in the diagnostic algorithm.

Why PCOS is a diagnosis of exclusion

PCOS is only diagnosed once other conditions with similar symptoms have been ruled out. This is not a bureaucratic extra step, but the core of a clean diagnosis.

Irregular cycles, acne or increased hair growth can also have other causes. That is why clarification includes at least the TSH value (thyroid), prolactin (an elevated prolactin level disturbs the cycle) and 17-OH progesterone, which can reveal a so-called late-onset adrenal hyperplasia, a congenital adrenal gland disorder that closely resembles PCOS. In cases of very high androgen levels or rapidly progressing symptoms, Cushing's syndrome or rare androgen-producing tumours are also considered.

You can read about how closely the thyroid and cycle are connected in our article Thyroid and cycle. Only once these alternatives are off the table and at least two Rotterdam criteria remain fulfilled is the diagnosis of PCOS truly certain.

Also checking for insulin resistance

Many women with PCOS have insulin resistance, and the international guideline recommends considering blood sugar early on. If body weight is elevated, an oral glucose tolerance test (oGTT) is recommended; otherwise, fasting glucose and the long-term value HbA1c are often sufficient.

The reason lies in a cycle that reinforces itself: when there is too much insulin in the blood, it stimulates the ovaries to produce more androgens, and at the same time it lowers the binding protein SHBG, so that more free testosterone becomes active. The elevated androgens in turn disrupt ovulation, which explains the cycle disturbance. This closes the loop: insulin, androgens and anovulation are mechanistically linked, which is why blood sugar already plays a role at diagnosis and not only later.

Important to know: insulin resistance does not only affect women with higher body weight. Slim women with PCOS can also be affected, which is why blood sugar is worth a look regardless of body mass index. More on this in our article Insulin resistance in women.

Special considerations for adolescents

Stricter rules apply to adolescents: here only the first two criteria count, cycle disturbance and hyperandrogenism, and both must be present together. Ultrasound and AMH are explicitly not recommended for diagnosis.

There is a good reason for this. In the first years after the first period, irregular cycles are often completely normal, and multifollicular ovaries are very common at this age without any underlying condition. In adolescence, an ultrasound would therefore falsely classify many healthy girls as abnormal. As a test, too, AMH is considerably less accurate in adolescents than in adults (van der Ham et al., 2024), which is why it is not used for diagnosis in this age group. That is why, when the picture is unclear, it is better to wait and reassess than to assign a label prematurely.

What helps after the diagnosis

The diagnosis is not an endpoint, but a starting point. Once it is clear that PCOS is present, it is about an individual plan of lifestyle, cycle protection and, where sensible, targeted supplementation. The foundation is always movement, blood-sugar-friendly eating and good sleep, because they act directly on insulin sensitivity.

Among the supplementary ingredients, inositol is the best studied. It acts as a so-called insulin sensitiser and thus targets exactly the loop of insulin and androgens that plays a central role in PCOS. A systematic review and meta-analysis of 26 RCTs with 1,691 women observed that inositol may increase the likelihood of a regular cycle by a factor of 1.79 compared with placebo (Greff et al., 2023). At the same time, the large analysis prepared for the 2023 guideline classifies the overall evidence cautiously and describes it as still limited (Fitz et al., 2024). The studies therefore point in an encouraging direction without being a promise. You can read in detail how inositol works in Myo-inositol for PCOS: effects, studies and dosage.

Zinc is also a topic. Zinc supplementation has been studied in women with PCOS: a randomised controlled trial observed favourable effects on androgen-related skin symptoms such as increased hair growth (Jamilian et al., 2016), and a recent meta-analysis observed an improvement in metabolic markers, including fasting glucose (Taslim et al., 2024). The evidence is still limited and does not replace treatment. For the nutrient itself, the approved EFSA statements apply: zinc contributes to normal fertility and reproduction and to the protection of cells from oxidative stress. Our Cycle+ Formula combines myo- and D-chiro-inositol with zinc and selected polyphenols, developed as a supplement for women with cycle concerns. It does not replace medical treatment, but can meaningfully support your foundation.

When to see your doctor

An appointment is worthwhile if your cycle is persistently irregular, your period repeatedly fails to appear, you suffer from acne, increased hair growth or hair loss, or if a wish to have children is not being fulfilled. Even if you feel that your symptoms have never been looked at in context, that is a good reason to specifically ask for a structured work-up.

The better prepared you are, the more focused the conversation will be. It helps to bring the following things:

• An overview of your cycle lengths and missed periods, ideally from a cycle app.
• Any existing test results, ultrasound findings and a list of your medications or contraception.
• Your most important question that you would like answered more clearly after the appointment, such as fertility, skin or metabolism.

You can find a comprehensive overview of causes, symptoms and treatment in our large PCOS guide, and which complaints lie behind the various forms is shown in Understanding PCOS symptoms: the 4 PCOS types.

Conclusion

Diagnosing PCOS does not mean finding a single value, but rather interpreting a pattern. The Rotterdam Criteria require at least two out of three characteristics: menstrual irregularity, hyperandrogenism, and polycystic ovaries or, since 2023, an elevated AMH level. In addition, other causes such as thyroid dysfunction, elevated prolactin, or adrenal hyperplasia must be ruled out.

If you've felt for years that something isn't right, there's no need to panic, but it is a reason for a structured clarification. With the right questions and good preparation, a vague suspicion can turn into a clear diagnosis, and from that diagnosis, a plan that suits you.