Uridine diphosphate glucuronosyltransferase 1A4 (UGT1A4) is a phase II drug metabolizing enzyme that plays an important role in the conjugation of various xenobiotics and endogenous compounds. In the context of vitamin D metabolism, conjugation of 25-hydroxyvitamin D3 (25(OH)D3), the main circulating form of vitamin D, may function as a pathway to help facilitate the enterohepatic circulation of vitamin D. Allele variants of the UGT1A4 gene are reported to contribute to inter-individual differences in enzyme activity, with the UGT1A4*3 variant gene product exhibiting increased glucuronidation activity. Previous work in our lab evaluated the polymorphic glucuronidation of vitamin D using human liver microsomes isolated from liver samples that were procured by St. Jude Children’s Research Hospital and University of Washington. The study found that carriers of the UGT1A4*3 allele showed increased 25(OH)D3 glucuronidation activity. While the samples used in this previous work was limited to a smaller subset of livers with the UGT1A4*3 genotype, we sought to further our investigation to include gene expression data obtained through RNA-Seq analysis and UGT1A4 protein quantification in LC-MS data. In addition, the current analysis was expanded to include a significantly greater portion of both the St. Jude and UW liver banks. From this study, we hope to gain greater insight into the impact that the *3 allele may have on the RNA and protein expression of UGT1A4. In addition, by assessing the relationship between UGT1A4*3 genotype and 25(OH)D3 glucuronidation, we may develop a better understanding of factors that may contribute to the variability in the biliary excretion and/or plasma levels of vitamin D glucuronides.