Red flags Chronic weight loss Chronic fever or night sweats Generalized lymphadenopathy Muscle weakness or pain Serious nonfatigue symptoms (eg, hemoptysis, hematemesis, severe dyspnea, ascites, confusion, suicidal ideation) Involvement of > 1 organ system (eg, rash plus arthritis) New or different headache or loss of vision, particularly with muscle pains, in an older adult Interpretation of findings In general, a cause is more likely to be found when fatigue is one of many symptoms than when fatigue is the sole symptom.