Vitamin D3 has a role in many autoimmune diseases and appears to play a function in controlling Rheumatoid Arthritis (RA). The aim of this study is to evaluate the relationship between serum level of vitamin D and RA disease activity score. The serum level of vitamin D in 75 RA patients referred to the rheumatology clinic of Rasoul-Akram hospital was measured. Patients were classified into low,...