OBJECTIVES: The rate and extent of utilization of IV iron in anemic CKD patients was quantified. Predictors of IV iron and ESA use were determined. The impact of IV iron and ESA use was examined separately for total hospital costs and length of stay (LOS). METHODS: This is a retrospective cohort analysis within the UHC data warehouse in the period of January 1, 2006, to December 31, 2008. Inclusion criteria were age > 18 years with a primary/secondary diagnosis of CKD. The exposure of interest was IV iron and ESA therapy, and the outcome was the difference in total hospital costs and length of stay. A binomial logistic regression using the GEE methodology was used to identify predictors of IV iron utilization. Propensity scores were used to control for confounding. A GEE model using gamma distribution and log link was used to determine the adjusted hospital cost and length of stay for the IV iron and ESA and ESA alone therapy groups. RESULTS: 82,947 patients met the study criteria. Of the 82,947 CKD patients on ESA therapy, only 8% (n = 6678) patients were on IV iron supplementation. Age, race, primary payer, admission status, severity of illness, dialysis status and physician specialty were identified as strong predictors of IV iron use.For patients using both IV iron and ESA (n=6678), mean costs were $34,756 compared to $31,404 for ESA users alone (n=76,269). The overall mean LOS for all patients was 9.75 days. For those using IV iron, the LOS was 10.71 days, and for those only using ESA, the LOS was 9.66 days. CONCLUSIONS: Our investigation showed significant reduction in ESA doses with the use of IV iron supplementation, however, the overall prevalence of IV iron usage was low. Intravenous iron users were associated with a higher total hospital cost and longer length of stay than ESA users.