Increased bilirubin load		Decreased bilirubin conjugation	Impaired bilirubin excretion
Hemolytic causes		Characteristics: increased unconjugated bilirubin level, normal percentage of reticulocytes Physiologic jaundice Crigler-Najjar syndrome types 1 and 2 Gilbert syndrome Hypothyroidism Breast milk jaundice	Characteristics: increased unconjugated and conjugated bilirubin level, negative Coombs' test, conjugated bilirubin level of >2 mg per dL (34 μmol per L) or >20% of total serum bilirubin level, conjugated bilirubin in urine Biliary obstruction: biliary atresia, choledochal cyst, primary sclerosing cholangitis, gallstones, neoplasm, Dubin-Johnson syndrome, Rotor's syndrome Infection: sepsis, urinary tract infection, syphilis, toxoplasmosis, tuberculosis, hepatitis, rubella, herpes Metabolic disorder: alpha1 antitrypsin deficiency, cystic fibrosis, galactosemia, glycogen storage disease, Gaucher's disease, hypothyroidism, Wilson's disease, Niemann-Pick disease Chromosomal abnormality: Turner's syndrome, trisomy 18 and 21 syndromes Drugs: aspirin, acetaminophen, sulfa, alcohol, rifampin (Rifadin), erythromycin, corticosteroids, tetracycline
	Characteristics: increased unconjugated bilirubin level, >6 percent reticulocytes, hemoglobin concentration of <13 g per dL (130 g per L) Coombs' test positive: Rh factor incompatibility, ABO incompatibility, minor antigens Coombs' test negative: red blood cell membrane defects (spherocytosis, elliptocytosis), red blood cell enzyme defects (G6PD deficiency, pyruvate kinase deficiency), drugs (e.g., sulfisoxazole acetyl with erythromycin ethylsuccinate (Pediazole), streptomycin, vitamin K), abnormal red blood cells (hemoglobinopathies), sepsis
Nonhemolytic causes
	Characteristics: increased unconjugated bilirubin level, normal percentage of reticulocytes Extravascular sources: cephalohematoma, bruising, central nervous system hemorrhage, swallowed blood Polycythemia: fetal-maternal transfusion, delayed cord clamping, twin-twin transfusion Exaggerated enterohepatic circulation: cystic fibrosis, ileal atresia, pyloric stenosis, Hirschsprung's disease, breast milk jaundice