In conventional endocrinology, adrenal fatigue is not an officially recognised diagnosis. The adrenal glands are either functioning normally or are in a state of adrenal insufficiency, which is a serious and measurable condition often caused by autoimmune disease or long-term steroid use.

However, in functional medicine, adrenal fatigue is used to describe a subclinical state of HPA axis dysregulation—where the brain-adrenal connection is disrupted due to chronic stress. Patients may experience:
Low morning energy and difficulty waking
Afternoon crashes or reliance on caffeine
Poor stress tolerance and emotional volatility
Sleep disturbances and light sleep
Cravings for stimulants or salty foods

These symptoms may stem from poor sleep hygiene, overtraining, chronic psychological stress, or nutritional depletion (especially B vitamins, magnesium, and vitamin C). While not a formal diagnosis, the concept helps guide lifestyle and nutritional interventions that support adrenal resilience.