Citrin deficiency (CD) is an underdiagnosed and understudied condition characterized by several distinct phenotypes: 1) neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD), 2) the adaptation or silent period, 3) failure to thrive and dyslipidemia form of CD (FTTDCD), and 4) citrullinemia type II (CTLN2), with the latter representing the final and most severe form of the condition. There is currently no cure for CD and patients manage their symptoms with lifelong dietary intervention and regular checkups with their physicians. A major hurdle in developing effective treatments for CD is the lack of effective biomarkers that track well with disease severity or measure the effectiveness of therapeutics. The present study aims to identify robust circulating biomarkers of CD through analysis of blood samples from CD patients.