From the Guidelines
The normal limits for Alanine Transaminase (ALT) levels in adults are 29 to 33 IU/L for men and 19 to 25 IU/L for women. ALT is an enzyme primarily found in liver cells that helps convert proteins into energy for the liver cells. When liver cells are damaged or die, ALT is released into the bloodstream, causing blood levels to rise. This is why ALT is considered a marker of liver health and is routinely measured as part of liver function tests. Elevated ALT levels may indicate liver damage from various causes including viral hepatitis, alcohol consumption, certain medications, or non-alcoholic fatty liver disease.
According to the most recent study 1, the severity of abnormal aminotransferase can be classified as mild, moderate, or severe, with moderate and severe being discussed collectively due to significant clinical overlap. The study also notes that ALT elevations are specific for liver injury owing to low concentrations in skeletal muscle and kidney.
It's worth noting that previous studies, such as 1, have suggested that the upper limit of normal (ULN) for ALT should be lower than previously established limits, with values of 30 IU/mL for men and 19 IU/mL for women. However, the most recent study 1 provides the most up-to-date and accurate information on normal ALT levels.
In clinical practice, any abnormal ALT result should be interpreted by a healthcare provider within the context of the patient's overall health status and other laboratory findings. Minor elevations can occur temporarily due to strenuous exercise or certain medications without indicating serious liver problems.
Key points to consider:
- Normal ALT levels are 29 to 33 IU/L for men and 19 to 25 IU/L for women 1
- ALT is a marker of liver health and is routinely measured as part of liver function tests
- Elevated ALT levels may indicate liver damage from various causes
- Any abnormal ALT result should be interpreted by a healthcare provider within the context of the patient's overall health status and other laboratory findings.
From the Research
Normal Limits for Alanine Transaminase (ALT) Levels in Adults
The normal limits for Alanine Transaminase (ALT) levels in adults can vary depending on several factors, including the laboratory conducting the test and the individual's overall health.
- According to a study published in 2012 2, the upper limit of normal (ULN) for ALT activity was found to be 29 IU/L for men and 22 IU/L for women, based on data from the U.S. National Health and Nutrition Examination Survey.
- The study also found that the cut-off for 95% sensitivity was an ALT of 24 IU/L for men and 18 IU/L for women, while the cut-off for 95% specificity was ALT of 44 IU/L for men and 32 IU/L for women.
Factors Affecting ALT Levels
Several factors can affect ALT levels, including liver disease, alcohol consumption, and body mass index.
- A study published in 1989 3 found that ursodeoxycholic acid (UDCA) treatment was effective in lowering ALT levels in patients with hypertransaminasemia.
- Another study published in 2021 4 found that UDCA treatment normalized liver enzymes, including ALT, within the first 3 months of treatment in patients with nonalcoholic fatty liver disease.
Variations in Normal Limits
It's worth noting that the normal limits for ALT levels can vary depending on the laboratory and the specific test used.
- A study published in 1991 5 found that the effect of UDCA on serum liver enzymes, including ALT, was dose-dependent, with significant decreases in ALT levels observed at doses as low as 250 mg/day.
- A study published in 2011 6 found that the long-term effect of UDCA on laboratory liver parameters, including ALT, was maintained up to 15 years in patients with primary biliary cirrhosis.