My HR and BP both came down with the combination of extra electrolyte fluids, Florinef, and verapamil (for tachycardia -- I can't take beta blockers because I have asthma). I was told the raised BP and tachy were likely compensation for low blood volume. It certainly sounds like you should be checked for diabetes insipidus. Even if it is DI, desmopressin only works in some forms, so you'll need to have some lab tests to sort out what kind you have. Let's hope you've found a treatable cause for some of your symptoms. Every little bit helps in the quest for improved quality of life.