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Labs determine 'normal range' by surveying the people using that lab. For my lab, normal ALT is 6-34 and normal AST is 9-34. ALT is made in the liver so high levels indicate it is being leaked out of damaged liver cells into the bloodstream.
^ Back to top. Normally, levels of ALT in the blood are low. Very high levels of ALT (more than 10 times normal) are usually due to acute hepatitis, sometimes due to a viral infection. In acute hepatitis, ALT levels usually stay high for about 1-2 months but can take as long as 3-6 months to return to normal.ST and ALT are considered to be two of the most important tests to detect liver injury, although ALT is more specific to the liver than is AST. Sometimes AST is compared directly to ALT and an AST/ALT ratio is calculated.