The Cortisol (8:00 AM) test is the essential baseline measure of your body's primary 'stress' hormone. Cortisol naturally follows a 'diurnal rhythm'—it is highest in the morning to wake you up. This 8:00 AM blood draw is the critical first step to see if your body is producing the correct peak amount. It's essential for investigating adrenal gland disorders like Addison's (too low) or Cushing's (too high). This is the foundational test for assessing your body's energy and stress-response system.