The purpose of this study is to investigate efficacy of oral thin film (OTF) cholecalciferol (vitamin D3) replacement in hematopoietic stem cell transplantation (HSCT) recipients who failed to achieve or sustain adequate vitamin D levels after vitamin D supplementation using current standard of care, or those unable to take/tolerate currently available enteral vitamin D formulations. With oral thin film (OTF) cholecalciferol, investigators hope to significantly improve the ease of administration, restoring compliance and facilitating therapeutic vitamin D levels without relying on the gut for absorption.
