You've probably heard the statistic before. It’s the one people toss around at dinner parties or in heated Twitter threads: 1.7%. They say that the percentage of people who are intersex is about the same as the number of redheads in the world.
It sounds tidy. It sounds definitive. But honestly? It’s a lot more complicated than a single number.
Biological sex isn't always a binary "this or that" situation. Sometimes, nature likes to color outside the lines. When we talk about intersex people, we’re talking about folks born with sex characteristics—chromosomes, hormones, or anatomy—that don’t fit typical medical definitions of "male" or "female."
But where did that 1.7% come from? And why do some scientists argue the "real" number is actually much, much lower?
The big debate over the 1.7 percent figure
Back in 2000, a researcher named Anne Fausto-Sterling and her colleagues at Brown University published a landmark study. They reviewed decades of medical literature and concluded that if you count every variation where a body deviates from the "Platonic ideal" of male or female, you land on that 1.7% figure.
It was a huge moment.
The United Nations eventually picked up this number. Advocacy groups used it to show that intersex variations aren't "rare" or "disorders" but are a natural part of human diversity.
But here’s the thing. Not every doctor agrees with what counts as intersex.
Why the numbers vary so much
Some researchers, like Leonard Sax, argue that the 1.7% number is way too broad. He published a rebuttal in 2002, claiming the "true" prevalence is closer to 0.018%.
Why the massive gap? It’s all about the definition.
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Sax argues that conditions like Klinefelter syndrome (XXY) or Turner syndrome (XO) shouldn't be counted as intersex because most people with these conditions don't have "ambiguous" genitals at birth. In his view, "intersex" should only apply when the physical appearance of the body doesn't match the chromosomes, or when the anatomy is visibly "neither" or "both."
Fausto-Sterling, on the other hand, says biological sex is a spectrum. If your chromosomes aren't XX or XY, you’re part of that variation.
It’s basically a clash between a narrow clinical definition and a broader biological one.
Common variations and their real-world frequency
When we look at the percentage of people who are intersex, we aren't looking at one single "condition." It’s an umbrella term for dozens of different variations.
Some are incredibly rare. Others show up more often than you'd think.
- Late-Onset Adrenal Hyperplasia (LOCAH): This is actually quite common, appearing in about 1 in 50 to 1 in 100 people in certain populations. It often isn't even noticed until puberty or later.
- Klinefelter Syndrome (XXY): This affects about 1 in 500 to 1 in 1,000 people assigned male at birth. Many men go their entire lives without knowing they have an extra X chromosome.
- Androgen Insensitivity Syndrome (AIS): This happens when a person has XY chromosomes but their body doesn't respond to testosterone. They often grow up appearing female. This occurs in roughly 1 in 20,000 births.
- Turner Syndrome (X): Affecting about 1 in 2,500 people assigned female at birth, this involves a missing or partially missing X chromosome.
Most intersex people look just like anyone else. You've likely walked past several today.
The "Redhead" comparison: Is it accurate?
You'll see this comparison everywhere. "Intersex people are as common as redheads!"
Is it true?
Well, it depends on which side of the 1.7% debate you land on. Red hair occurs in about 1% to 2% of the global population. If you accept the Fausto-Sterling estimate, then yes, the comparison holds water.
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But if you use the stricter 0.018% definition, intersex variations are much rarer—more like 1 in 5,500 people.
Regardless of the "exact" number, the point advocacy groups are making is that this isn't some freak occurrence. Millions of people globally have bodies that don't fit the standard binary.
Why the data is still so messy in 2026
Collecting data on intersex populations is a nightmare for statisticians.
First, many people are never "diagnosed." If you have XXY chromosomes but never struggle with fertility or health issues, you might just live your life thinking you’re a typical guy.
Second, the history of medicine here is... dark.
For decades, many intersex infants were subjected to "normalizing" surgeries shortly after birth. Doctors often told parents not to tell the child about their status. This "cloak of silence" means thousands of adults today are intersex and have no idea. They might just know they had a "corrective surgery" for a hernia or a "undescended testicle" as a baby.
Furthermore, different cultures see this differently. In some parts of the world, intersex variations are highly stigmatized, leading to underreporting. In others, they are simply seen as a medical "glitch" to be fixed rather than an identity to be counted.
What we’re learning from modern surveys
We're finally getting better data because researchers are starting to ask the right questions.
A 2025 study from the European Union Agency for Fundamental Rights found that when you ask people to self-identify, the numbers shift again. In their survey, they found that intersex individuals often face significant discrimination in healthcare and the workplace.
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They also found a high overlap between the intersex community and the LGBTQ+ community, though the two are not the same thing. Being intersex is about biological sex traits, not who you’re attracted to or how you identify your gender.
But because intersex people's bodies are "different," they often find community in queer spaces.
Navigating the medical vs. social model
The debate over the percentage of people who are intersex isn't just about math. It’s about how we treat human beings.
The Medical Model views intersex variations as "Disorders of Sex Development" (DSD). This framework often prioritizes "fixing" the body to fit into the male/female binary.
The Social Model (or Human Rights Model) views intersex as a natural variation of human biology. It argues that the "problem" isn't the person's body, but a society that refuses to acknowledge a spectrum.
When you hear 1.7%, you're usually hearing the Social Model. When you hear 0.02%, you're hearing the strict Medical Model.
Actionable steps for understanding intersex health
If you’re trying to make sense of these numbers for yourself or a loved one, keep these points in mind:
- Don't get hung up on one statistic. Whether it's 1.7% or 0.02%, intersex people exist and deserve autonomy over their own bodies.
- Language matters. Many people prefer the term "intersex," while others prefer "DSD" or specific diagnostic names like MRKH or CAIS. Always follow an individual's lead.
- Check the source. If you see a number, look at what it includes. Does it include chromosomal variations? Does it only count "ambiguous" genitalia? The definition changes the result.
- Prioritize bodily autonomy. Most major human rights organizations, including the World Health Organization, now advocate for delaying non-emergency surgeries on intersex children until they can participate in the decision.
- Look for community-led data. Organizations like interACT or the Intersex Community Trust often provide more nuanced insights than older medical textbooks.
The world is finally moving away from trying to force every body into one of two boxes. Understanding the true scale of human biological diversity is the first step toward better healthcare and basic respect for everyone, regardless of their chromosomal makeup.
The data might be messy, but the reality is clear: humanity is a spectrum.
Next Steps for Further Insight:
- Examine the specific health guidelines provided by the World Health Organization (WHO) regarding the management of intersex variations.
- Research the history of the Intersex Society of North America (ISNA) to understand how advocacy has shaped current medical ethics.
- Review the 2023-2025 census data from countries that have begun including "non-binary" or "intersex" markers to see how self-identification rates are changing in real-time.