Not sure if this is in the right section, and I was talking about it in another thread - but I think I was hijacking that thread and have some other specific questions so I started this one. I've been trying to understand orthostatic intolerance and found Dr. Bell's info about 5 sub-types: http://www.pediatricnetwork.org/medical/CFS/bell-commentary/oi-intro.htm I did the poor men's tilt table test today and found that I can stand for 30 mins. After that, I quickly feel dreadful and need to sit IMMEDIATELY or feel like I could faint. I had to make a chart of my BP readings and heart rate (taking every 5-10 mins) to make sense of it all. Nothing showed up immediately upon standing, that's why I've never thought I had POTS. And POTS is the easiest to find info about. My systolic rate stays the same throughout, but my diastolic rate is all over the place. It is working it's butt off to keep me standing (ping ponging up and down). The longer I stand the higher my heart rate climbs, then finally it starts to drop again when the the diastolic rate drops more quickly. I can fit in POTS category if I go by Dr. Bell's info: "A healthy person will not change their heart rate standing up for an hour. In a person with POTS, the heart rate increases 28 beats per minute (bpm). Some experts say the heart rate should exceed 120 bpm to have POTS. But either way, this increase occurs frequently in CFS. I think the increase in heart rate is linked to the decrease in blood volume. (Orthostatic intolerance has been called Idiopathic hypovolemia in the past)" My heart rate only got up to 90 bpm (not 120) and I was starting to feel pretty awful. It only went up 25 bpm before I really wanted to lay down and then it started to fall as the diastolic rate fell too. But I think the HR raising is because it's trying to compensate for the diastolic hypotension. Dr. Bell said "This represents a fall in the lower number of the BP, and seems to be the least frequent abnormality in patients with CFS I have tested." I was wondering does anyone else on the forum have this particular OI problem? What is Neurally mediated hypotension then in his listings, because he doesn't use that term in his article. But NMH and POTS are most 'popular' when searching the net, I couldn't find a lot of info about Orthostatic diastolic hypotension alone for example.