Background and Aims: Vitamin D deficiency is common among patients with inflammatory bowel disease, even when the disease is in remission. This study was designed to evaluate the serum levels of 25-hydroxy vitamin D [25(OH)-D3] in patients who suffered from ulcerative colitis and the control group in Golestan province in the northeast of Iran. Methods: In this case-control study, 60 patients with a definite histopathological diagnosis of ulcerative colitis were included. The control group was selected from healthy blood donors. The serum levels of 25(OH)-D3 were measured by the ELISA method (ids- UK). Data were entered into the SPSS-16 software and were analyzed by t-test and Chi-square test. Results: The mean serum level of vitamin D in the patients was significantly lower as compared to that in the control group (P-value <0.01). The differences in the levels of 25-OH-D3 were statistically significant between the two sexes, in both groups. A normal vitamin D level was seen in all cases with proctitis, in 20% of cases in the rectosigmoiditis group and in no cases in the pan-colitis group. The difference was statistically significant (p-value <0.01). Conclusions: It can be concluded that the serum levels of vitamin D in the patients with ulcerative colitis are low and that inflammatory bowel disease can be a target for the specific vitamin D therapy
