Your body uses ALT to break down food into energy. Normally, ALT levels in the blood are low. If your liver is damaged, it will release more ALT. Most lower-level ALT results indicate a healthy liver. However, studies have shown that lower-than-normal results have been related to increased long-term mortality.
The normal value for ALT in blood ranges from 29 to 33 units per liter (IU/L) for males and 19 to 25 IU/L for females, but this value can vary depending on the hospital
What then is an elevated ALT level? The lack of standardization among laboratories is part of the problem. Different labs can define anywhere from 40 to 65 U/L as normal.
Very high levels of ALT (more than 10 times normal) are usually due to acute hepatitis, sometimes due to a viral hepatitis 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.