OBJECTIVES/SPECIFIC AIMS: The aim of this study is to compare intestinal phosphorus absorption in healthy adults and moderate stage chronic kidney disease patients in the context of a controlled feeding study METHODS/STUDY POPULATION: Participants are 30-75 years old and include 10 healthy subjects and 10 moderate-staged CKD patients. Each subject pool will be enrolled in a 9-day study period including 7 days of controlled feeding of a 1500 mg phosphorus diet. Following the controlled feeding, two days of absorption tests will take place (oral and IV tests) utilizing radioisotopic phosphorus to calculate fractional absorption efficiency. RESULTS/ANTICIPATED RESULTS: Current enrollment has produced 7 total matched subject (current n = 14/20). Four of the 7 pairs of completed subjects are female and 3 of 7 are black. Preliminary kinetic modeling data from the first enrolled subject show a moderate CKD patient with fractional absorption of 0.375. With forthcoming analyses, we expect that this fractional absorption result will not be statistically different from this subject’s matched pair, nor will each groups average absorption be different from the other. Additionally, we expect absorption to be maintained even with changes in secondary outcomes measures in serum (FGF23, 1,25-dihydroxyvitamin D, parathyroid hormone, and total phosphorus) in CKD patients. DISCUSSION/SIGNIFICANCE OF IMPACT: Lack of statistical difference in fractional phosphorus absorption between gropus would support that intestinal phosphorus absorption is inappropriately normal in CKD patients compared to healthy adults, despite evidence of abnormal phosphorus homeostatic mechanisms. Future studies will consider the effect of dietary P restriction, the most common nutrition intervention in moderate stage CKD, on fractional absorption efficiency in CKD.