How to Measure Your Cortisol Levels

Salivary and hair cortisol levels are routinely used as a biomarker of psychological stress related to mental or physical diseases. It's been shown that the association between chronic stress and cortisol changes during the first hour of post-sleep in the morning so salivary cortisol was found to be elevated in chronically stressed subjects from this review. i'm wondering too because until you brought this up today i hadn't realized you could measure cortisol through hair unlike do you think hair would give you a more long-term average than a blood or saliva test  i know it can fluctuate within a 15 minute span of acute stress but i'm wondering if a hair would almost be like the hba1c