How reliable are these tests, saliva vsl. blood.?

My blood test showed seratonin levels extremely low.
My dr.put me on 5-HTP 25mg. starting than up to 50mg.

I recently read on Dr. Ray Sahelian MD. wedsite cortisol,that a 45 day study was performed on people who were given large amounts of 5-HTP and the saliva test results showed increased levels of cortisol.

Interesting, my several test results showed high levels.
Yet in past years, tests were low. Yet, my symptoms are still extreme fatigue, intolerance to minor stress even,
anxiety associated with stress.
Yet, I stillcan have a low blood sugar attack,how can this be if cortisol is elevated, does not cortisol raise blood sugar levels.

Paul