(a–j) Plasma metabolites and ratios differ significantly between chronic kidney disease (CKD) cohorts (stages 2 and 3b; n = 20/group; false discovery rate <0.05). ADMA, asymmetric dimethylarginine; Cit, citrulline; Cr, creatinine; C4:1, butenoylcarnitine (fatty acylcarnitine); FDR, false discovery rate (5% of significant tests will result in false positives); Kyn, kynurenine; Orn, ornithine; PC ae (C32:1), phosphatidylcholine with acyl-akyl residue; Pro, proline; SDMA, symmetric dimethylarginine; Trp, tryptophan; Tyr, tyrosine.