Cerilliant® Snap-N-Spike® solutions include most routinely tested bile acids and their stable-labeled internal standards. Certified reference materials consist of lithocholic acid, taurocholic acid, and native and deuterium-labeled analogs of cholic acid, chenodeoxycholic acid, deoxycholic acid, and ursodeoxycholic acid. Mass spectrometry-based analyses of bile acids are performed in neonatal screening of inborn errors of BA synthesis and therapeutic monitoring of patient responses to therapy.