There's a tilt test where they put you on a bed and then go from lying position to standing. Measure blood pressure and heart rate. They had to stop mine after a few minutes because they thought I was going to pass out based on my readings, not on how I was feeling, which wasn't out of the ordinary for me!

They can give you beta blockers and fludrocortisone (think that's what it's called) to slow heart and increase fluids. I didn't notice a difference, bar the beta blockers making me sleepy. Maybe there are other things that people use that help? I don't find it a problem (compared with the TOS pain!), although it's a little worrying that heart rate goes from 75 to 161 just from lying down to walking...

Told to drink lots and eat salt, which I've always done a lot of. Says on my summary will find standing or sitting for long periods difficult and being in crowded places (why??)

Saw someone for autonomic dysfunction who referred me for tilt test, in case you're wondering re referral route. Probably different in the US?