The burden of chronic disease is continuing to rise. Even though patients may be in remission or have quiescent disease, several studies have confirmed that symptoms, such as e.g., fatigue, is troublesome.Previous studies have confirmed that vitamin D deficiency is associated with both Crohn's disease and Rheumatoid Arthritis. Since Vitamin D is associated with both onset of chronic disease and energy, we aim in this study to assess its impact on fatigue in various chronic diseases.