A systems biology approach was used to comprehensively examine the impact of renal disease and hemodialysis (HD) on host response during critical illness. We examined the metabolome, proteome, and transcriptome of 150 patients with critical illness, stratified by renal function. Plasma metabolite values showed greater changes as renal function declined, with the greatest derangements in patients receiving chronic HD. Specifically, 6 uremic retention molecules, 17 other protein catabolites, 7 modified nucleosides, and 7 pentose phosphate sugars increased as renal function declined, consistent with decreased excretion or increased catabolism of amino acids and ribonucleotides. Similarly, the proteome showed increased levels of low-molecular weight proteins and acute phase reactants. The transcriptome revealed a broad-based decrease in mRNA levels among HD patients. Systems integration revealed an unrecognized association between plasma RNASE1 and several RNA catabolites and modified nucleosides. Further, allantoin, N1-methyl-4-pyridone-3-carboxamide, and n-acetylaspartate showed inverse correlations with the majority of significantly down-regulated genes. In conclusion, renal function broadly affected the plasma metabolome, proteome, and peripheral blood transcriptome during critical illness. These changes were not effectively mitigated by hemodialysis. These studies suggest several novel mechanisms whereby renal dysfunction contributes to critical illness. Overall design: We sequenced peripheral blood RNA of 133 representative subjects with systemic inflammatory response syndrome that had Acute Kidney Injury (AKI) or Hemodialysis (HD). No injury (AKI0; n= 58); AKI Stage 1 (AKI1; n= 36); AKI stage 2 and 3 (AKI23; n= 17); HD (N=22).