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.

The primary aim of this study is to investigate whether or not there might be an association between levels of vitamin D and the subjective experience of fatigue in conditions, such as inflammatory bowel disease, diabetes mellitus, rheumatoid arthritis and irritable bowel syndrome.

Secondary aims is to study both the co-occurence and influence of pain, depression and anxiety.

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.

The primary aim of this study is to investigate whether or not there might be an association between levels of vitamin D and the subjective experience of fatigue in conditions, such as inflammatory bowel disease, diabetes mellitus, rheumatoid arthritis and irritable bowel syndrome.

Secondary aims is to study both the co-occurence and influence of pain, depression and anxiety.

Inclusion Criteria:

• informed consent,
• over 18 years of age

Exclusion Criteria:

• dementia,
• cognitive disorders,
• not able to comply with the study procedures,
• on active vitamin D treatment

Patients with an established diagnose of IBD, DIA, IBS or RA is eligible for inclusion in this study. Patients must be over 18 years of age. Disease activity will be measured using the SCCAI for ulcerative colitis, SCDAI for Crohn's disease, DAS-28 for rheumatoid arthritis. In Dia and IBD objective activity measures, such as calprotectin in stools and HbA1C, will be collected.