To evaluate fatigue, like pain, as a medical complaint requires attention to dimensions of sensation and affect. Patients come to the doctor with complaints about fatigue when they believe that there has been a change from the usual. As with other symptoms in medicine, taking a history means first understanding the complaint from the worldview of the patient. The first 5 minutes of the patient's description of the complaint gives data for many hypotheses. How did he or she come to recognize it? Why did he or she come to the doctor now? What precipitates fatigue, what perpetuates it, and what relieves it? What are the parameters that describe the symptom? How much effort does it take to get going? What is the quality of sleep? We know that disordered sleep can alter energy.