Diagnosed With PCOS as a Teen? Why It’s Worth a Second Look

By Dr. Mélanie DesChâtelets, ND. Licensed naturopathic doctor and founder of PMOS Health Collective.

If you were diagnosed with PCOS as a teen, there’s something worth knowing: the rules used to diagnose PMOS (formerly PCOS) before age 20 are different from the adult ones, and stricter. A teenage body is still finding its rhythm, so some features that look like PCOS at 15 are just a normal phase. That’s why a label given years ago is worth a second look now, not to second-guess your care, but to make sure you’d actually have met the adolescent criteria in the first place. Here’s how to check.

One quick convention before we start: I’ll use age 20 as the line between the teen rules and the adult rules, just to keep it simple. The real line is about 8 years after your first period. For most of you that lands around 20, for some a little sooner or a little later. So whenever you see 20 in here, read it as shorthand for that 8-year mark.

And one quick note. This is education, not medical advice, and I’m not your naturopathic doctor. Read it, take notes, then bring your history to your own care team.

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Why teen diagnosis works differently

In the years right after a first period, the communication between the brain and the ovaries is just getting started. So some things that look like PCOS in a teenager are actually normal for the stage. That’s also why PCOS can look so different from one person to the next, and why a teen label given years ago deserves a recheck. To avoid over-diagnosing during a normal phase, the criteria are stricter before age 20. If you were diagnosed back then, the first thing to know is that the bar was supposed to be higher, not lower.

The adolescent rule: two of two, not two of three

Before age 20, there’s no reliable way to assess ovarian morphology, so ultrasound and AMH are off the table. That turns the adult “two out of three” rule into a stricter “two out of two.” You need both: irregular cycles (defined specifically for teens, below) and androgen signs, either symptoms or bloodwork. If only one of the two was present, that isn’t a full diagnosis. It can be considered “PCOS at risk,” but only once other causes for the symptoms have been explored first. So when you look back at your file, the question is: did I clearly have both?

Reading the androgen box as a teen

The visible signs come first: aggressive acne that doesn’t respond well to treatment or persists as you get older, hair thinning where the part keeps widening, or excess hair on the face tracking toward the belly button or down the legs.

Here’s a clinical pearl worth carrying, especially in hindsight: in PCOS, high-androgen symptoms tend to come on slowly and progressively. If excess facial hair showed up very suddenly and very severely, that can point to other causes and deserves a different workup. So if your symptoms came on fast back then, that’s worth raising clearly with your provider now, so the right testing gets done.

The cycle definitions change by year

This is the part defined differently than for adults, and it hinges on how many years it had been since your first period. In the first year, irregular cycles are normal. From one to under three years out, cycles shorter than 21 days or longer than 45 days count as irregular. At three years and beyond, the window tightens to shorter than 21 or longer than 35. And at any point more than a year out, a single cycle of 90 days or more counts. So “my cycles were irregular as a teen” only means something against the right year-based window. Worth checking which window you were actually in.

Why a teen ultrasound doesn’t count

You may have had a pelvic ultrasound back then for any number of reasons, but for diagnosing PCOS it isn’t reliable until it’s been about 8 years since your first period (which for many lands around age 20). Before that, the ovaries normally show more follicles, so the scan can look “polycystic” when nothing is wrong. So if your teen diagnosis was hanging mostly on an ultrasound, that’s the single biggest reason to revisit it and check whether the other two criteria were actually met.

“PCOS at risk,” and when to reassess

Some teens have a few features but not quite enough for a clear diagnosis: maybe some irregular cycles but little on the androgen side, or the reverse. Once other causes are ruled out, that’s “PCOS at risk.” Not a no, not a yes, a “let’s keep an eye on this.” The recommendation is to reassess once it’s been at least 8 years since the first period (around age 20 for many), when ovarian morphology testing finally becomes accurate, either by ultrasound or by AMH if you’d rather skip an internal scan.

So if you’re carrying a teen label into adulthood, the empowering move is simple: pull your records, see whether you met two of two, and bring it to your provider as a clear question. “I was diagnosed as a teen. Looking at the adolescent criteria, can we confirm I still meet a PCOS diagnosis now?” Whether the answer is a yes, a not-yet, or a watch, knowing exactly where you stand is the whole point, because every decision after it depends on getting this part right.

Watch the full video: Is This Really PCOS? Teen Edition, and subscribe to my YouTube channel.

This article is educational, not medical advice or a diagnosis. If something here resonates, bring it to your healthcare team, who can look at it through the lens of your individual health.

Main references

1. Teede HJ, et al. Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. J Clin Endocrinol Metab. 2023. PubMed