Fatigue is a term used to describe an overall feeling of tiredness or lack of energy. It isnt the same as simply feeling drowsy or sleepy. When youre fatigued, you have no motivation and no energy. Being sleepy may be a symptom of fatigue, but its not the same thing.Fatigue is a common symptom of many medical conditions that range in severity from mild to serious. Its also a natural result of some lifestyle choices, such as lack of exercise or poor diet.If your fatigue doesnt resolve with proper rest and nutrition, or you suspect its caused by an underlying physical or mental health condition, see your doctor. They can help diagnose the cause of your fatigue and work with you to treat it.