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Aspartate Aminotransferase, Serum/Plasma — Substance Concentration

Published: August 9, 2026Updated: August 16, 2026

An AST blood test measures aspartate aminotransferase in serum or plasma. It is mainly used to assess liver injury but can also rise with muscle damage.

Quick summary

["Elevated AST may indicate liver or muscle injury and should be interpreted with other laboratory results."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
26600-7
Short code
AAA SerPl-sCnc
Synonyms
AAA SerPl-sCnc
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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?

Aspartate aminotransferase, commonly called AST, is an enzyme found in many tissues, with the highest concentrations in the liver and skeletal muscle. This test measures AST in serum or plasma, the liquid portion of blood.

Why might I need this test?

AST is often ordered as part of a liver panel or when symptoms suggest liver disease. Your clinician may also order it to evaluate possible muscle injury or monitor the effects of medicines that can affect the liver.

How is the test performed?

A healthcare professional draws a blood sample from a vein. The sample may be allowed to clot to produce serum or placed in a tube with an anticoagulant to produce plasma, and the laboratory then measures AST using a validated assay.

How do I prepare for the test?

Fasting is usually not required, but follow any specific instructions from your clinician or laboratory. Inform the healthcare team if you recently had intense exercise, as strenuous activity can temporarily increase AST.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

AST

Frequently asked questions

Is AST the same as ALT?
No. AST and ALT are different liver enzymes that are often measured together. AST is also present in muscle, so it is less specific to the liver than ALT.
Does a high AST always mean I have liver disease?
No. Muscle injury, recent intense exercise, injections, and some medicines can also raise AST. Your clinician will interpret the result alongside your symptoms, medical history, and other laboratory tests.
Does this test require fasting?
Usually not. Fasting may be requested when AST is part of a larger panel or when your clinician gives specific preparation instructions.
  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 16, 2026. · Read our editorial policy