I finally got a PoTS diagnosis last year (along with ASD and ADHD), at 39.
Lying down for 5 minutes then standing up for 10 - if the pulse gets and remains high but with a low blood pressure, that's the main diagnostic criteria.
Symptoms include head rushes, gray outs, brain fog, fainting in like 8%, fatigue, temprature intolerance to hot and cold, cold exteremities, bladder issues e.g. needing to pee more than average ("PoTS bladder"), palpitations as in feeling your pulse (not aythmia) and maybe even rocking/stimming to it (I got great muscle control from trying to cover it up for so long, great for dancing).
Things that help are certain postures, staying hydrated, increasing salt intake by x8 to help the body retain water, leggings or compression socks.
Apparently there are other drugs, but you will be explaining it to most medical folk you meet. I'm waiting for a cardio referral in the UK, though ultimatly it's an autonomic system issue so I would have thought neurology, but we will live and learn.
Possibly maybe I had EDS; zebras keep saying I have such smooth skin and move in a hypermobile way, though I don't pass the standard over-stretch tests, but praying upward behind my back is no problem what-so-ever.
https://en.wikipedia.org/wiki/Postural_orthostatic_tachycard...
I've just realised I might have "amplified musculoskeletal pain syndrome" also, which is something I had been planning bringing up. I didn't know how to factor the chronic "unable to ever relax" pain underlying everything in.