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Is your ALT normal for your age?
A flagged or “normal” ALT blood test result only makes sense beside the age, sex and lab behind it.
Why one range doesn’t fit every age
Children’s upper limits are lower than many hospital ranges, adult limits depend on sex, and average ALT falls in older adults. Labs differ too: published adult ranges include 4–36, 7–56 and 10–49 U/L.
Where to start
- Your own result: read the adult section, then the tier steps.
- Your child’s result: start with the children and teens section.
- A parent’s result: go to the older adults section.
For what the number means at any age, see our full guide to reading an ALT result.
ℹ️ Medical Disclaimer: This article covers reading ALT lab results, children’s results, follow-up testing and emergency symptoms. It is general education, not diagnosis or treatment advice. Review any result with your primary care clinician, your child’s pediatrician, or a gastroenterologist or hepatologist before acting; call 911 for emergencies.
What is a normal ALT level at each age?
No single ALT value is normal at every age; the table separates healthy-population cutoffs, guideline limits and routine lab ranges.
The age-by-age chart
| Age group | Upper limit (U/L) | Basis and source | Key Clinical Detail |
|---|---|---|---|
| Under 18 months | 60 boys, 55 girls | 95th percentile in healthy children (England 2009) | Highest values in childhood |
| After 18 months | 40 boys, 35 girls | Same study | Lower in teens |
| Ages 12–17 | About 26 boys, 22 girls | Screening cutoff (NASPGHAN pediatric guideline, 2017) | Below many hospital limits |
| Adults | 29–33 men, 19–25 women | Guideline healthy limit (American College of Gastroenterology [ACG], 2017) | Labs often print wider ranges |
| Older adults | No separate limit found | Average ALT lower (Rancho Bernardo 2010) | One hospital lab prints 10–49 for all adults |
How to read the basis column
A percentile cutoff describes healthy children, a guideline limit is a recommendation, and a lab range is what prints on your report. Start with your own lab’s range, then use the rows as context.
Normal ALT in children and teens
Pediatric limits sit lower than many hospital ranges.
Why teen cutoffs run lower than hospital ranges
A survey reported children’s hospital limits from 30 to 90 U/L, median 53. The SAFETY study limits are about 26 U/L for boys and 22 U/L for girls aged 12–17, and the NASPGHAN pediatric guideline advises these sex-specific limits over each lab’s own. Cutoffs still vary with the reference group; a later cohort reported 95th percentiles of 24–29 U/L (girls) and 29–32 (boys).
NASPGHAN advises evaluating an ALT that stays above twice the limit for more than 3 months; an ALT above 80 U/L warrants timely evaluation, which is a prompt-visit threshold, not a diagnosis.
What parents should ask the pediatrician
✅ Patient Action: Ask your child’s pediatrician: “Which upper limit did you use, and should we repeat this test before deciding anything?” If it persists, ask about a pediatric gastroenterologist.
For the next steps after a high result, see our guide to high ALT in children for parents.
Normal ALT for adults: what labs show vs guidelines
Adult limits are given by sex, and labs often print wider ranges.
Guideline limit vs lab range
The ACG guideline defines a healthy ALT level as 29–33 IU/L for men and 19–25 IU/L for women and advises assessing anything above. Each lab sets its own range from the population it serves.
Why men and women differ
ALT is higher in men than women, and the guideline also notes it rises in a straight line with body mass index. Check yours with our BMI calculator, and see women’s healthy ALT range and menopause for the midlife shift.
Does ALT drop as you get older?
In population studies, average ALT is lower in older adults.
What the cohort data show
In the Rancho Bernardo cohort of 2,364 adults aged 30–93, mean ALT was 23, 21, 20 and 17 IU/L across four age quartiles. A follow-up analysis found ALT also fell within the same people over time, independent of metabolic traits and alcohol use. Whether this reflects liver-cell loss or function remains undetermined.
Is a low ALT in older adults a problem?
A lower number does not prove a healthier liver, since the ACG notes a normal ALT may not exclude significant liver disease. The sources reviewed describe no guideline-endorsed ALT limit for older adults; see what low ALT levels mean for a flagged low result.
✅ Patient Action: Ask your parent’s primary care clinician: “Does the trend matter more than this one value?”
What to do with your ALT result at any age
Your result divided by your lab’s upper limit shows how far above normal it sits.
Find your tier
The ACG guideline calls results under 2 times the limit borderline, 2–5 times mild, 5–15 times moderate and over 15 times severe, and advises repeating the panel before a full workup. For a child, ask the pediatrician which thresholds apply.
Questions to bring to the appointment
- Which upper limit did you use, and how many times above it am I?
- Should we repeat the test before ordering anything else?
When a “normal for your age” ALT isn’t the full story
A normal ALT may not exclude significant liver disease, according to the ACG.
Liver disease can exist with a normal ALT
So symptoms or risk factors still deserve a clinician’s review even when your number looks normal for your age.
Signs that shouldn’t wait
⚠️ Clinical Warning: Acute liver failure, meaning rapid liver injury with a prolonged clotting time and confusion from liver dysfunction, requires immediate evaluation regardless of the ALT level, per the ACG. New confusion needs same-day medical care; call 911 if someone is confused and hard to wake.
✅ Patient Action: Ask your primary care clinician: “Since my ALT is normal, do I need other liver tests?”
ALT levels by age: your questions answered
1. What are normal ALT levels by age?
Normal ALT levels by age differ: children’s cutoffs run lower than many hospital ranges, adult limits depend on sex, and averages fall in older adults.
2. What is a normal ALT level for a child?
A normal ALT level for a child after 18 months is up to 40 U/L (boys) or 35 (girls); ask your pediatrician which limit applies.
3. What is a normal ALT for a teenager?
A normal ALT for a teenager is 26 U/L or lower for boys and 22 or lower for girls (NASPGHAN); ask your pediatrician.
4. What is a normal ALT level for adults?
A normal ALT level for adults is 29–33 IU/L for men, 19–25 for women (ACG); ask your clinician which limit applies.
5. Does ALT go up or down with age?
ALT tends to go down with age: mean levels fell from 23 IU/L at ages 30–62 to 17 IU/L at ages 78–93.
6. What is a normal ALT for older adults?
A normal ALT for older adults has no separate guideline limit in the sources reviewed; averages run lower, so trends matter. Ask the clinician.
7. Is normal ALT different for men and women?
Yes. Normal ALT differs by sex: the ACG sets 29–33 IU/L for men and 19–25 for women.
8. Why do labs use different ALT ranges?
Each lab sets its ALT range from the population it serves, so printed adult ranges differ, such as 4–36 or 10–49 U/L.
9. Is a low ALT normal in older adults?
Average ALT falls with age, so a low ALT in older adults is not unusual; ask the clinician if it is flagged.
10. Can ALT be normal with liver disease?
Yes. A normal ALT may not exclude significant liver disease at any age, so symptoms or risk factors still warrant a clinician’s review.
11. When should a child’s high ALT be checked?
NASPGHAN advises evaluating a child’s high ALT when it stays above twice the limit for over 3 months, or exceeds 80 U/L; call the pediatrician.
Your next step
ALT has no single normal across a lifetime: children’s cutoffs run lower than many hospital ranges, adult guideline limits split by sex, and averages drift down in older adults. Bring your exact number and your lab’s range to your clinician.
About this content
How this article was put together: researched from recognised health sources, drafted with the help of AI tools, and edited by hand, with sources linked throughout.
Sameer Patel is the founder and editor of My Medicine Advisor. He is not a doctor or medical professional — before starting this site he worked in banking,…
Medical disclaimer
The content on MyMedicineAdvisor is provided for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Health information on this website should not be used to diagnose, treat, cure, or prevent any condition without guidance from a qualified healthcare professional. Always seek the advice of your doctor, physician, or another licensed healthcare provider with any questions you may have regarding a medical condition, symptoms, medications, or treatment decisions.
