joegrane
Check out this.
http://www.canaryclub.org/adrenal-article-980/706-cortisol-1-or-4.html
A friend got an AM blood cortisol on the same day. Both blood and saliva were very similarly normal; however saliva cortisol was low the reminder of the day.
Don't forget other related hormones--DHEA, progsterone, pregnenolone and downstream sex hormones. They are commonly studied in blood.
Joe