Class of 2015 Abstract / Objectives: The primary objective of the study was to evaluate for change in vitamin D levels and regimens in cystic fibrosis (CF) patients following implementation of the 2012 Cystic Fibrosis Foundation (CFF) vitamin D guidelines. Secondary endpoints included clinician adherence to guideline recommendations for treatment and management of vitamin D deficiency. Methods: This retrospective chart review included CF patients with 25-hydroxy vitamin D (25(OH)D) levels from University of Arizona Medical Center (UAMC) between April 1, 2011-March 31, 2012 and July 1, 2012-June 30, 2013. Total 25(OH)D levels and vitamin D regimens were collected along with data on respiratory cultures, pulmonary function, and hospitalizations. Data were analyzed by Student’s T-tests and chi square analyses. Results: A total of 62 patients were included in the study. Mean 25(OH)D levels did not significantly differ between the study periods (28.9±10.5 ng/mL pre-guideline and 27.0±9.1 ng/mL post-guideline, p=0.158). Cholecalciferol use increased post-guideline (57.1%) versus pre-guideline (75.8%, p=0.027). Post-guideline cholecalciferol doses increased to 2836.5±2669.4 international units [IU] daily compared to 1518.0±912.0 IU daily pre-guideline (p<0.001). Clinician adherence to dose titration recommendations resulted in significant 25(OH)D level elevations (28.3±8.9 ng/mL versus 24.7±9.0, p=0.047). Conclusions: The prescribing pattern of clinicians significantly changed to reflect vitamin D regimens suggested by CFF guidelines. This finding suggests that had sufficient time been allowed following guideline implementation, a significant difference in 25(OH)D levels would have resulted. Additional research is needed concerning the effect of the guidelines on vitamin D status, clinical outcomes, and comorbidities.