Low serum cortisol is a marker of adrenal depletion. There are several symptoms of low cortisol levels, although they are vague and often related to other disorders. Some symptoms include:
Fatigue
Unrefreshing sleep
Ill-defined malaise
Loss of ambition
Increased fear and apprehension
Scattered thinking
Decreased concentration and memory
Short fuse
Hypoglycemia symptoms
Sugar cravings
Slow recovery from illness
Allergies or autoimmune disease
Increased achiness or arthritis
Nausea/no appetite in a.m.
Excessive consumption of caffeine or other stimulants
Tendency to feel best towards evening
Decreased sex drive