An 18 year old alanine aminotransferase 135 U/L is not normal and suggests mild hepatocellular damage. Normal values for alanine aminotransferase are usually 0 to 40 U/L. 135 U/L alanine aminotransferase at 18 years of age is an elevated value and suggests the presence of liver cell damage. Hepatocellular damage can be caused by medications, viral infections such as hepatitis B, alcoholic hepatitis caused by heavy drinking, and fatty liver caused by long-term high-fat diet. Hepatitis virus test and abdominal ultrasound can be performed under the guidance of the doctor to further clarify the cause of the disease. At the same time, if you suspect that it is caused by drugs, you can consult your doctor whether you can stop using drugs, quit drinking alcohol, and eat a light diet if you have a fatty liver. If necessary, follow the doctor’s instructions to use drugs to protect the liver treatment, so as not to aggravate the condition.