p-Cresol glucuronide is a metabolite of p-cresol, a uremic toxin formed by bacterial fermentation of proteins in the large intestine. It is formed from p-cresol primarily by the UDP-glucuronosyltransferase (UGT) isoform UGT1A6, but also by UGT1A9, in human liver and kidney microsomes. p-Cresol glucuronide accumulates in feces, blood, and urine of patients with chronic kidney disease (CKD).