The cortisol awakening response is the natural rise in cortisol that is seen 30 to 40 minutes after awakening followed by a noticeable drop by 60 minutes. CAR can be utilized as a biomarker for assessment of the HPA axis function in routine clinical practice. CAR is influenced by overall HPA reactivity, as well as a person’s anticipation of stress.
The CAR involves a measure of the percent rise in cortisol from awakening to 30 minutes post-awakening and the expected decline in cortisol seen at 60 minutes. The Diurnal Cortisol Profile involves 4 cortisol samples taken at 30 minutes post-awakening, noon, dinner time, and bedtime. While the CAR can provide the best information on HPA axis reactivity and function, the Diurnal Cortisol Profile can identify dysregulation in the natural cortisol circadian rhythm. 
Useful for:
Feeling stressed 
Fatigue 
Insomnia 
Nervousness/Irritability 
Salt/Sugar cravings 
Dizzy spells 
Headaches 
Decreased stamina 
Burn out 
Chronic disease 
Anxiety/depression