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 slices · age and sex · 1 source
Filed under panels: Liver Function , Metabolic Panel · topics: Liver , Metabolic
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.
Population Distribution
Browse by Demographic
| Age (years) | male (U/L) | female (U/L) |
|---|---|---|
| 20-29 | 10–76.6 (22) | 8–39 (14) |
| 30-39 | 12.7–69 (24) | 8–48 (14) |
| 40-49 | 13–56 (24) | 8–39 (14) |
| 50-59 | 12–60 (25) | 10–43 (18) |
| 60-69 | 10–50 (20) | 10–39 (17) |
| 70+ | 9–39.7 (18) | 9–31 (14) |
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.