Vitamin D is a potent steroid hormone that induces widespread changes in gene expression and controls key biological pathways . Here we review pathophysiology of vitamin D with particular reference to COVID-19 and pancreatic cancer . Utility as a therapeutic agent is limited by hypercalcemic effects and attempts to circumvent this problem have used vitamin D superagonists, with increased efficacy and reduced calcemic effect . A further caveat is that vitamin D mediates multiple diverse effects . Some of these (anti-fibrosis) are likely beneficial in patients with COVID-19 and pancreatic cancer, whereas others (reduced immunity), may be beneficial through attenuation of the cytokine storm in patients with advanced COVID-19, but detrimental in pancreatic cancer . Vitamin D superagonists represent an untapped resource for development of effective therapeutic agents . However, to be successful this approach will require agonists with high cell-tissue specificity.