Can this result diagnose a condition on its own?

No. Laboratory results are interpreted with symptoms, medical history, specimen conditions and related tests.

Which reference range should I use?

Start with the performing laboratory's own reference interval; clinical cutoffs, when relevant, are separate sourced thresholds used for a specific purpose.

When should I discuss the result with a healthcare professional?

Results that are clearly outside range, persistent, symptomatic or unexpected should be reviewed by a healthcare professional.

Information about a laboratory test

Low ALT: What Does It Mean?

Low ALT is usually less clinically important than an elevation and is interpreted with the laboratory range and overall context.

Test summary

Test name: ALT
Abbreviations: ALT, ALAT, GPT
Category: Hepatology / Liver Enzymes
Panel: Liver Function Panel
Specimen: Serum / plasma
Common units: U/L, µkat/L

What does the test measure?

Measures blood activity of ALT, an enzyme found mainly in liver cells.

Why is the test ordered?

Usually ordered with AST, ALP, GGT and bilirubin to assess possible liver-cell injury and to monitor liver-related conditions or medicine effects.

Information about a low result

Low ALT is usually less clinically important than an elevation and is interpreted with the laboratory range and overall context.

Information about a high result

High ALT can occur with liver-cell injury; the degree of elevation and the pattern with AST, ALP, GGT and bilirubin matter.

Reference and clinical context

Start with the performing laboratory's reference interval, unit and specimen conditions. Numeric information on this page is stored as sourced example intervals or clinical thresholds.

Reference range 1

>= 4 – <= 36 U/L

Population: Adults
Age range: 18
Specimen: Serum / plasma

Example adult ALT reference interval

The source presents these values as a common example reference interval. Laboratory method, age and clinical context can change the range; the user's own report takes priority.

Reference ranges may vary by laboratory, method used, age, sex, pregnancy status, and clinical context. The reference range on your own laboratory report takes precedence.

Interpretation notes

A single ALT value does not identify a specific liver disease. Results are interpreted with other liver tests, medicines, alcohol exposure, symptoms and medical history.

Related specialties

Gastroenterology
Internal Medicine
Family Medicine

Frequently asked questions

Sources

Liver Function Tests — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · Liver panel components, purposes, pattern-based interpretation and limitations · Verified: Aug 12, 2026
Comprehensive Metabolic Panel — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · Example adult intervals for ALT, AST, ALP, albumin, bilirubin, total protein, BUN, creatinine and electrolytes · Verified: Aug 12, 2026
ALT Blood Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · ALT purpose, liver-cell injury context and example interval · Verified: Aug 12, 2026
AST Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · AST purpose and interpretation with ALT/other liver tests · Verified: Aug 12, 2026
Gamma-glutamyl Transferase (GGT) Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · GGT purpose and interpretation with ALP and other liver tests · Verified: Aug 12, 2026