Lack of energy is common and underestimated, and its importance is an under-rated medical complaint. Daytime fatigue can be transient or chronic. Often times people with persistent and disabling fatigue show no clinical or laboratory signs of illness, leading to a frustrating search for a definable cause, diagnosis, and treatment plan for their fatigue. Many vitamins, minerals, herbs and accessory nutrients support mitochondrial production of energy, or sex hormone and adrenal hormone energy production. Additionally, supplements that improve sleep or the relaxation response may also help improve daytime energy levels.