My 15 year old son (SW) has had problems with good control for quite sometime due a very fast metabolism.  He has had umpteen 17 OHP and cortisol blood profiles done over 24 hours, (blood taken every two hours for 24 hours).  It was explained to me that they do pre dose to check if the suppression is lasting until the dose and then 2 hours after as this is when the cortisol is at its highest from ingestion of the tablet.  A lot of endo’s here in the UK prefer to do the blood tests pre dose, some who do blood spots do it pre dose for 24 hours whereas others insist if the morning pre-dose levels are tested then the rest of the days levels will be fine.  Having studied my sons results it certainly isn’t the case with him.  However saying that I have heard of some endo’s who do not do regular testing at all.  I do wish the endocrinologists would set a proper protocol and also agree on what an optimum 17 OHP level should be.