My wife Liz, 20 years with ME, always reported " a real high" when placed on a saline drip when visiting hospital for treatment. The Consultant, now retired, considered low blood volume to be a possible cause for this, not just the re-hydration after a long journey. Reviewing her blood pressure readings (after I'd been found to have high blood pressure so considering this area), I noticed her PULSE pressure is always quite low (resting pressure test) compared to normal. On researching this I find one reason to be "low blood volume". Are you monitoring, or have access to your blood pressure readings? Subtract the lower reading from the higher - 40 is normal, anything around 25 is "quite low". If this level IS predominant in ME sufferers it could be of significant help in diagnosis. Let's see.