Introduction: ALT/AST enzymes are present inside the cells. AST is found in cardiac and skeletal muscle and red blood cells but the ALT is checked mainly in the liver. In general, the rise of these two indicators shows liver damage. The usual measurements of these enzymes are used in liver function tests, but the levels of AST and ALT do not always reflect liver function. Method and Cases: 17 cases of liver dysfunction transiently were evaluated clinically, biochemically, and imaging study of sonogram in pediatric in-patients for 3 years. Result: Most common causes of transient liver dysfunction were infection, especially viral gastroenteritis, and bacterial infection interfering oral food intake. More often occurred in the children who have infant hyperbilirubinemia, positive history of mitochondrial dysfunction or hypoglycemia. Fasting study in one case of hypoglycemia patient showed reversible liver dysfunction during fasting over 20 hours fasting. Discussion: A significant increase in AST and ALT with normal bilirubin can be observed in clinically healthy people during blunt trauma, viral infection, severe pain, metabolic syndrome, fasting or accidental health screening.