AST Blood Test (Aspartate Aminotransferase)
The AST blood test measures aspartate aminotransferase, an enzyme present in the liver, heart, muscle, and several other tissues. It is a routine component of liver-focused testing and is almost always interpreted alongside ALT rather than alone.
About this test
AST works inside cells across several tissues. The liver holds a large share, but muscle — including heart muscle — carries meaningful amounts too.
AST appears on many standard panels as well as being orderable on its own. A clinician typically reads it in context: alongside ALT, sometimes with GGT or other liver-associated markers, and always against the person's circumstances — recent exercise, medications, and history all matter.
Who might consider this test?
- AST is often looked up after it appears flagged on a routine panel, since it is part of many standard chemistry groupings.
- People also order it together with ALT to follow liver-associated markers over time with their clinician.
- Interpretation should always rest with a licensed clinician who knows your full picture.
Test details
| Quest code | 822 |
|---|---|
| Methodology | Spectrophotometry |
| Sample type | 1 mL serum |
| Collection | Quest patient service center |
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Quest resources
Additional details
How AST differs from ALT
The two enzymes overlap, but ALT is concentrated mainly in the liver while AST is spread across liver, heart, skeletal muscle, and other tissues. That difference is exactly why they are ordered together: the relationship between the two results helps a clinician think about which tissue might be contributing and what to check next.
Neither enzyme is read as a verdict on its own. Patterns over time, and the company each result keeps, carry the meaning.
Muscle matters for AST
Because skeletal muscle contains AST, hard workouts and muscle injury can influence a result. Someone who trained heavily in the days before a blood draw may see that reflected, which is one of the most common benign explanations clinicians consider before anything else.
Ordering AST through Celio Health
AST can be ordered on its own or alongside ALT and other liver-associated markers in a single visit, and a physician order is included with every purchase — no separate appointment is needed beforehand. Sample collection happens at a participating Quest Diagnostics patient service center, and most results return within a few business days as a secure PDF.
If you are building a broader picture, the test menu includes related panels that bundle AST with the markers it is usually interpreted against, which keeps everything to one blood draw and one combined report.
Order online and a physician order is included — no doctor's visit and no insurance needed. Your sample is collected at a Quest Diagnostics patient service center.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What is AST in a blood test?
AST (aspartate aminotransferase) is an enzyme found in the liver, heart, muscle and other tissues. The test measures the amount circulating in blood.
What is the difference between AST and ALT?
ALT is concentrated mostly in the liver, while AST also comes from muscle and other tissues. Clinicians read them together because the pair is more informative than either alone.
Can exercise affect an AST result?
Yes. Because muscle contains AST, strenuous workouts in the days before a draw can influence the result — one of the most common benign explanations clinicians consider.
Do I need to fast before an AST test?
AST itself does not generally require fasting, though panels that include it sometimes do. Follow the instructions on your requisition.
Can I get the AST test without a doctor's visit or insurance?
Yes. The $15 cash price includes an independent physician's order, so no referral is needed, and insurance is never involved.