Normal ALT Levels by Age: Charts & Reference Ranges
ALT normal ranges are not one-size-fits-all. Age, sex, and body composition all influence what is considered a healthy ALT level. This guide provides normal ALT levels by age to help you interpret your lab results more accurately.
ALT Normal Range by Age Group
| Age Group | Males (U/L) | Females (U/L) |
|---|---|---|
| Newborns | 10–50 | 10–50 |
| Children (1–12) | 10–35 | 10–35 |
| Adolescents (13–17) | 10–45 | 10–40 |
| Young adults (18–40) | 10–56 | 7–45 |
| Middle-aged (41–60) | 10–50 | 7–40 |
| Older adults (61+) | 10–45 | 7–38 |
Why Does ALT Change with Age?
ALT tends to be highest in newborns and young adults, then gradually declines with age. Several factors explain this pattern:
- Liver size — the liver is proportionally larger in children and young adults
- Muscle mass — ALT correlates somewhat with muscle and liver mass, both of which decline with age
- Metabolic rate — higher metabolic activity in youth can produce slightly higher enzyme levels
- Medication use — older adults taking multiple medications may see modest ALT changes
Should Older Adults Have a Lower "Normal" Range?
Some hepatologists argue yes. Research suggests that ALT levels above 30 U/L in men and 19 U/L in women — even if within the standard lab range — may indicate early fatty liver disease. This is particularly relevant for older adults, where even mild elevations can signal metabolic dysfunction.
What If My Child Has a High ALT?
Children can have temporarily elevated ALT due to viral infections, obesity, or certain medications. Persistent elevation in children warrants evaluation for NAFLD, which is increasingly common in pediatric populations.
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