A patient seated in the chair before a blood draw
In person

AST

An enzyme from the liver and muscles, read with ALT, from one draw.

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  • 2,000+ lab locations. Find one near you
  • Nothing due at the lab. FSA / HSA accepted
  • Ordered by a licensed clinician

At a glance

Collection
Blood draw
A standard blood draw at the lab.
Preparation
None
Nothing to do ahead of time. Water is fine.
Results
1 to 2 days
Typical turnaround after your visit.
Where
2,000+ lab locations
Nationwide, with nothing due at the lab.

About this test

AST (aspartate aminotransferase) is an enzyme found in the liver, heart, and muscles, with smaller amounts in other tissues. When any of these are injured, AST can rise in the blood. Because it is less liver-specific than ALT, the two are usually read together. No fasting is needed.

For adults 18 and older. Test availability varies by lab location.

Who should take this test?

Often read alongside ALT, this test is for adults checking liver health or following up on a past AST result, with a healthcare provider helping to read the pair.

Ask about this test

Not sure this is the right test?

AI-generated. For information only, not medical advice. Call 911 for an emergency.

What does this test measure?

Your result shows how much AST is in your blood and, read with ALT, can help a healthcare provider judge whether a rise is more likely from the liver or from muscle.

Aspartate aminotransferase (AST)
AST is an enzyme found in your liver and also in your heart, muscles, and other tissues. When these cells are injured, AST leaks into the blood. Hard exercise, muscle strain, and some medicines can raise it, so it is read together with ALT and your other results.
Why it’s measured: An enzyme that rises when liver or muscle cells are under stress.

How it works

  1. Step 1

    Order online

    Check out here. A licensed clinician in your state reviews your order and sends it to the lab.

  2. Step 2

    Visit a lab

    Bring a photo ID to any of 2,000+ lab locations. No fasting needed, and nothing is due at the lab.

  3. Step 3

    Get your results

    Results post to your account, usually in 1 to 2 days, each number next to the lab’s reference range.

Find a lab near you

Choose from 2,000+ lab locations nationwide. Your order works at any of them.

What your results tell you

AST is reported as enzyme activity in units per liter (U/L) and shown next to the lab’s reference range for comparison.

  • Your number next to the lab’s reference range
  • Explained in plain language
  • A licensed clinician reviews your order and, if appropriate, orders the test.
  • A lab report you can download and share

A high AST can come from the liver, muscle, or other tissues. A healthcare provider can explain what yours means and what to check next.

Clinical-grade testing, from the comfort of home.

From the lab to your report, every step of our process meets the gold standard in medical testing.

  • CLIA-certified labs

    Every lab we partner with is certified under the Clinical Laboratory Improvement Amendments, meeting both state and federal standards with regular independent inspections.

  • We protect your health data

    We protect your health data with encryption and do not sell it. Some results must be reported to public health authorities by law. See our Privacy Notice.

  • Rigorous quality assurance

    All partner labs run regular internal quality checks, participate in proficiency testing, and comply with federal and state lab regulations.

  • Clinician-reviewed reports

    Results are reviewed by an independent, licensed clinician.

Questions

Common questions.

Anything else, our care team answers by phone, text, or email.

AST is found in several tissues, including the liver, heart, and skeletal muscle. ALT is found mostly in the liver. If AST is high and ALT is not, the rise may be coming from somewhere other than the liver.

Reading the two together gives a healthcare provider a clearer sense of where a high result is coming from.

It can. Muscles contain AST, and muscle injury releases it into the blood. A hard workout, heavy lifting, or a muscle strain shortly before your draw could raise the number.

If you exercised hard recently, mention it to the healthcare provider who reads your results. They may suggest a recheck.

Severe muscle pain or weakness with dark urine after hard exercise needs prompt medical care.

AST shows whether the enzyme level is raised, not why. It is not specific to the liver, and it is not a direct measure of how well the liver is working. A healthcare provider uses it with ALT, your other results, and your history to decide whether anything else is needed.

Lab tests are informational and don’t diagnose conditions on their own. Available to adults 18 and older; test availability varies by lab location. A licensed clinician reviews your order and, if appropriate, orders the test. All testing is performed at CLIA-certified laboratories. Not for emergencies: if you think you may be having a medical emergency, call 911.