Skip to content

Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST)

Published: August 9, 2026Updated: August 17, 2026

ALT and AST are blood enzymes commonly measured together to evaluate liver-cell injury and help guide follow-up testing.

Quick summary

["Abnormal ALT or AST results may indicate liver injury, but they can also result from muscle damage or other conditions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
103102-0
Short code
A alternata (rAlt a) 1 IgE RAST
Synonyms
A alternata (rAlt a) 1 IgE RAST
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
7
Ref high
56
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
rast
CPT
84484
SNOMED
302773008
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

This test measures the activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in a blood sample. These enzymes are found in liver cells, and ALT is somewhat more liver-specific than AST.

Why might I need this test?

ALT and AST may be ordered during a routine health check, when evaluating symptoms such as abdominal discomfort, jaundice, or fatigue, or when monitoring liver disease, alcohol use, or medications that may affect the liver.

How is the test performed?

A blood sample is collected and analyzed in a laboratory to measure ALT and AST enzyme activity. The results are usually reported with the laboratory's reference range and may be interpreted alongside other liver tests and your medical history.

How do I prepare for the test?

Fasting is often not required, but follow any instructions provided by the laboratory or your clinician. Tell the care team about alcohol use, supplements, and prescription or nonprescription medicines; do not stop medicines without medical advice.

Reference range

Adult males: 7-56 U/L; Adult females: 7-43 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings2

Short name

ALT and AST

Frequently asked questions

What does a high ALT or AST result mean?
It may indicate injury or inflammation in the liver, but AST can also be increased by muscle damage, intense exercise, alcohol, or some medicines. Your clinician will interpret the result with the rest of your evaluation.
Can ALT and AST be normal despite a liver problem?
Yes. Some liver conditions may not cause these enzymes to rise, and the degree of elevation does not always match the severity of disease. Other tests may be needed.
Do I need to fast before this test?
Often not, but laboratory instructions can vary. It is helpful to avoid heavy alcohol use and strenuous exercise before testing and to tell the care team about medicines or supplements you take.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy