Alanine aminotransferase 51 U/L is considered mildly elevated. Alanine aminotransferase, or alanine aminotransferase (ALT), has a normal value of 5-40 U/L, so 51 U/L is a mild elevation. Elevated values may be caused by liver diseases such as acute and chronic viral hepatitis, alcoholic liver disease, intra- and extra-hepatic cholestasis, etc. Acute myocardial infarction, skeletal muscle-related disorders such as dermatomyositis, and other systemic disorders such as pulmonary and renal infarctions may also lead to elevation of this enzyme. In addition, unhealthy diets and routines such as late nights, excessive consumption of fatty foods, and excessive alcohol consumption may also cause mild elevation of the enzyme. In conclusion, if physiological factors are excluded, it is recommended to consult a doctor in a timely manner and to follow up regularly to receive standardized diagnosis and treatment.