Alanine Aminotransferase (ALT)
ALT is consistently higher in males than females and is strongly right-skewed, with the upper tail widening in middle age as fatty liver disease and metabolic dysfunction become more prevalent.
Unit: U/L · 12 groups · age and sex · 1 source
Filed under panels: Liver Function , Metabolic Panel · topics: Liver , Metabolic
Alanine Aminotransferase (ALT) by age and sex
| Age (years) | Males (U/L) | Females (U/L) |
|---|---|---|
| 20-29 | median 21 middle 90% 9 to 72 | median 14 middle 90% 8 to 38 |
| 30-39 | median 23 middle 90% 12 to 64 | median 14 middle 90% 8 to 47 |
| 40-49 | median 24 middle 90% 13 to 61 | median 14 middle 90% 7 to 38.3 |
| 50-59 | median 25 middle 90% 12 to 54.9 | median 18 middle 90% 10 to 43 |
| 60-69 | median 20 middle 90% 10 to 50.6 | median 17 middle 90% 10 to 39 |
| 70+ | median 18 middle 90% 9 to 39 | median 14 middle 90% 9 to 30.9 |
Download Alanine Aminotransferase (ALT) percentiles (CSV) Values at full stored precision; tables on this site may round for display. Licensed under CC BY 4.0.
Population Distribution
Alanine aminotransferase (ALT) is a liver enzyme measured on the standard chemistry panel. These percentiles reflect the full US population rather than a screened healthy subgroup, so they include participants with fatty liver disease, alcohol-related liver injury, viral hepatitis, medication effects, and other causes of hepatocellular injury.
Frequently Asked Questions
Why is ALT right-skewed?
Most people have modest ALT values, but a smaller subgroup has steatotic liver disease, alcohol-related injury, viral hepatitis, medication effects, or other hepatic stress that pushes values much higher. That creates a long upper tail.
Why is ALT higher in males?
At the population level, males have higher average ALT because visceral adiposity, hepatic fat accumulation, and lifestyle exposures shift the distribution upward relative to females.
Are these clinical reference ranges?
No. These are population percentiles from NHANES, not screened healthy laboratory reference intervals. They describe where a value sits in the population distribution.
Data Sources
Cite this data
LabNorms. Alanine Aminotransferase (ALT) population percentiles by age and sex. Data: NHANES 2017-March 2020 Pre-Pandemic. https://labnorms.com/analytes/alt/. Licensed under CC BY 4.0. Accessed [date].
Download Alanine Aminotransferase (ALT) percentiles (CSV) Values at full stored precision; tables on this site may round for display. Licensed under CC BY 4.0.