From the ESHRE** Guideline for the Diagnosis and Treatment of Endometriosis:
… there is often a delay of up to 12 years between symptom onset and a definitive diagnosis.
Yep. Sounds about right.
**European Society for Human Reproduction and Embryology

Every time I hear this statistic I take a deep breath and think THANK FUCK IT WAS ONLY SIX YEARS FOR ME.
I’m very well-informed and surrounded by people who will come to medical appointments to advocate for me. I’m also lucky enough to have access to private healthcare as well as NHS care, else that delay would have taken longer.
Yup, the diagnostic delay really angers me because:
Yes, that’s about right, especially if symptoms show up at menarche (as mine did) and the kid then has to wait until adulthood because the parents don’t advocate for the kid. My mother was certain I was just being overly dramatic about pain so bad that it regularly caused me to pass out and throw up, the first two days of my period, every single month. “Everybody has pain with their periods; suck it up.”
Quite true. I was in the somewhat different circumstance of having parents who did advocate for me at the onset. However, enough doctors told us the “suck it up and deal” line — and independently, she didn’t know enough about endo to respond to that — that she started telling me, “it’s normal” — but only after so many health care providers told her the same thing.