GOALS To determine whether patients with celiac disease (CD) and low vitamin D levels also have a higher prevalence of other autoimmune diseases (AD) as compared with patients with normal vitamin D levels. BACKGROUND Patients with CD carry a higher risk of other autoimmune disorders. Because of its immunoregulatory properties, vitamin D deficiency has been proposed in the pathogenesis of a variety of AD. Whether low vitamin D levels in patients with CD can predict concomitant AD is unknown. STUDY A retrospective cross-sectional study of 530 adult patients with CD and a 25-hydroxyvitamin D level on record at Columbia University Medical Center. RESULTS One hundred thirty-three patients (25%) had vitamin D deficiency. The prevalence of AD was similar among those with normal vitamin D levels (11%), insufficiency (9%), and deficiency (12%, P=0.66). On multivariate analysis, adjusting for age of CD diagnosis and sex, vitamin D deficiency was not associated with AD (odds ratio, 1.35; 95% confidence interval, 0.62-2.95). The risk of psoriasis was higher in patients with vitamin D deficiency (7% vs. 3%, P=0.04). Vitamin D deficiency was more common in those who presented with anemia (39%) than in those who did not (23% P=0.002). CONCLUSIONS Vitamin D deficiency in CD is common but does not predict AD. The risk of psoriasis is increased in vitamin D-deficient CD patients. Assessment of vitamin D seems to be a high-yield practice, especially in those CD patients who present with anemia.