What Causes Low ALT Levels?

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Typically, low alanine aminotransferase (ALT) levels in the blood are considered normal, and it is high levels of ALT that should be cause for concern, according to Lab Tests Online. High ALT levels can be indicative of liver damage caused by hepatitis or cirrhosis, lead poisoning, exposure to carbon tetrachloride, necrosis (large tumor decay), mononucleosis and some medicinal use, including statins, antibiotics, chemotherapy, aspirin, narcotics or barbiturates, according to WebMD. Growth spurts in children can also lead to increase ALT levels.