Phenylalanine Blood Guthrie test: < 2 mg/day/L Fluorometry method Normal newborn: 1.2-3.4 mg/ dl Premature newborn: 2-7.5 mg/ dl Adult: 0.8-1.8 mg/ dl To detect PKU and other causes of hyperphenylalaninemia To monitor patients who have PKU and are being maintained on a phenylalanine-restricted diet; Elevated blood level of phenylalanine will cause central nervous system damage and mental retardation. PKU Severe burns Hyperphenylalaninemia Liver disease Sepsis Galactosemia Little to no ingestion of milk Insufficient quantity of blood Antibiotics