[Fatigue].

Many patients with fatigue do not visit a physician. In patients who do consult the general practitioner, the cause of their fatigue is explained in about a quarter: 8 percent has a somatic cause while psychosocial causes explain 16 percent. In about three quarters the cause of fatigue remains unexplained. Because of the low prevalence of somatic causes the general practitioner will be reluctant to perform additional examinations but a thorough physical examination is essential. In patients with a longer duration of fatigue (> 6 months) it is indicated to expand inquiries. This starts with extending history taking in the direction of consanguinity and hereditary diseases. More comprehensive blood tests and investigation of sleep are important further steps. Referral to a specialist is essential as specialists are more familiar with scripts of rare diseases. The prognosis of longer lasting fatigue is bad, especially in the case of fatigue meeting criteria for ME/CFS. Treatment of longer lasting fatigue could compromise of psycho-education, exercise and specific therapies for sleeping disorders.