Lethargy Definition Return to top A feeling of lack of energy, weariness or tiredness. Considerations Return to top Fatigue is not the same as drowsiness , but the desire to sleep may accompany fatigue. Fatigue represents a normal and important response to physical exertion, emotional stress , or lack of sleep.
Fatigue can also be a nonspecific symptom of a psychological or physiologic disorder.
Fatigue that is not relieved by normal means, or that occurs in the absence of a known cause or other symptoms should be medically evaluated. The pattern of fatigue may help delineate its underlying cause. Individuals who arise in the morning rested but, with activity, rapidly fatigue may have an ongoing condition or disease. Individuals who awaken fatigued and the level of fatigue remains constant throughout the day may be suffering from depression . However, these are not absolutes and chronic fatigue should be evaluated by a health care provider.