Polycystic ovary syndrome (PCOS) affects an estimated 10 to 13% of women of reproductive age worldwide. That figure comes from the World Health Organization and translates to roughly one in every eight to ten women. Perhaps more striking: up to 70% of those women remain undiagnosed, meaning millions are living with PCOS without knowing it.
Why Estimates Vary So Widely
If you’ve seen numbers ranging from 6% to 20% across different sources, the reason is simple: doctors don’t all use the same checklist to diagnose PCOS. Three sets of diagnostic criteria exist, and each one casts a different net. The broadest criteria (called the Rotterdam criteria) require two out of three features: irregular periods, elevated androgens (male-pattern hormones), and a specific appearance of the ovaries on ultrasound. Older, stricter criteria require both irregular periods and high androgens, leaving out women who have only one of those.
In one head-to-head comparison, the Rotterdam criteria identified PCOS in 63% of a study population, while the stricter NIH criteria identified it in only 23% of the same group. That’s a nearly threefold difference from the exact same women. The 10 to 13% global estimate reflects the most commonly used criteria today, but the number you encounter will depend on which definition a given study applied.
Prevalence by Ethnicity
PCOS doesn’t affect all populations equally. A large study of women receiving outpatient care in the United States found notable differences in diagnosed PCOS rates across racial and ethnic groups:
- South Asian women: 3.5%
- Hispanic women: 1.9%
- Black women: 1.7%
- Filipino women: 1.7%
- White women: 1.6%
- Chinese women: 1.1%
These numbers are far lower than the 10 to 13% global estimate, and that gap itself is telling. Because this study measured only formally diagnosed cases, it captures the underdiagnosis problem in real time. South Asian women had both the highest diagnosis rate and, according to broader population studies, some of the highest true prevalence. But every group listed here almost certainly has far more undiagnosed cases than diagnosed ones. Disparities in healthcare access, symptom recognition, and provider awareness all play a role in who gets a diagnosis and who doesn’t.
PCOS in Teenagers
Diagnosing PCOS in adolescents is trickier because irregular periods and hormonal fluctuations are normal during puberty. A 2024 systematic review pooling data from over 14,000 adolescents estimated a global prevalence of about 6 to 10%, depending on which diagnostic criteria were used. Under the most current international guidelines, which deliberately exclude certain ultrasound findings in teens to avoid overdiagnosis, the rate was 6.3%.
Geography matters here too. Prevalence among adolescents in Southeast Asia was around 11%, while in the Western Pacific region it dropped to about 3%. A single European study reported 4.3%. These regional differences likely reflect a combination of genetics, diet, obesity rates, and how aggressively clinicians screen for the condition in younger patients.
The Underdiagnosis Problem
The 70% undiagnosed figure is not just a footnote. It means that for every three women who know they have PCOS, roughly seven more do not. Several factors drive this gap. PCOS symptoms overlap with common complaints that are easy to dismiss: acne, weight gain, irregular periods, thinning hair. Many women assume these are just normal variations. Doctors sometimes treat individual symptoms (prescribing birth control for irregular periods, for instance) without investigating the underlying cause. And because PCOS has no single definitive test, diagnosis requires connecting multiple dots, something that can take years.
Women who are lean often face an additional barrier. PCOS is strongly associated with weight gain, so clinicians may not consider the diagnosis in someone with a normal BMI, even when other hallmark signs are present.
Insulin Resistance and Metabolic Effects
PCOS is not just a reproductive condition. Between 60 and 95% of women with PCOS have some degree of insulin resistance, meaning their bodies struggle to use insulin efficiently. This makes the condition a significant metabolic issue as well. The severity depends on the specific pattern of symptoms. Women with both irregular periods and high androgens tend to have insulin resistance rates around 80%, while those with milder presentations may be closer to 38%.
This insulin connection helps explain why PCOS raises the risk for type 2 diabetes, cardiovascular disease, and metabolic syndrome. It also means that lifestyle changes targeting blood sugar regulation, like regular physical activity and dietary adjustments, can meaningfully improve symptoms for many women.
Impact on Fertility
PCOS is one of the most common causes of difficulty getting pregnant, primarily because it disrupts ovulation. But the picture is more nuanced than many women fear. In the general population, about 85% of couples conceive within a year of regular unprotected sex. For women with PCOS, that number drops to about 50% in the same timeframe. That’s a significant reduction, but it also means half of women with PCOS conceive without any medical intervention within a year.
For those who need help, ovulation-inducing treatments are often effective. PCOS-related infertility is among the most treatable forms, and most women with the condition who want to become pregnant eventually do. The key variable is whether and how often ovulation occurs, which varies widely from person to person.