ALT and AST — Liver Enzymes
ALT and AST are enzymes measured on liver blood tests. An increased level is often a sign of liver disease, read against the lab's range and the other liver tests.
ALT and AST are enzymes measured on liver blood tests; an increased level is often a sign of liver disease, read against your lab's range and alongside the other liver tests. ALT is found mostly in the liver, while AST is also found in the heart and muscles.
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A mildly raised liver enzyme is the most common early signal of fatty liver.
Transcript & sources → All videosMr. Age is AgeGen's editorial character. Facts come from the protocol above.
The biomarker
- Name: ALT + AST
- Units: U/L
- Standard reference range: ALT 4–36; AST 8–33 (ranges vary by lab)
How to read your result
| Value | Interpretation |
|---|---|
| Within the lab's range | Read alongside the rest of the liver panel (ALP, bilirubin). |
| Above the lab's range | Often a sign of liver disease, more likely when other liver tests are also raised. Review with a clinician. |
| Outside the range — context | Does not always mean a condition that needs treatment: pregnancy, exercise, certain medicines, age and sex all affect results. |
| AST/ALT ratio > 2:1 | Per Cleveland Clinic, suggestive of alcohol-related liver disease; a clinician reads it together with GGT and your history. |
What moves the needle
- Testing. ALT and AST are usually run with other liver tests (ALP, bilirubin) — ask what the whole panel shows.
- Clinician. Discuss any result outside the lab's range with a clinician before drawing conclusions.
Why this test is worth asking for
- ALT is found mostly in the liver, so it checks more specifically for liver damage than AST, which is also found in the heart and muscles.
- ALT results can help tell sudden (acute) liver problems apart from long-term (chronic) ones.
- Both are usually part of a routine liver panel, and they are read together with ALP and bilirubin rather than on their own.
Related protocols
Sources
- MedlinePlus — ALT blood test
- MedlinePlus — AST test
- MedlinePlus Encyclopedia — ALT blood test
- MedlinePlus Encyclopedia — AST blood test
- Cleveland Clinic — Liver test interpretation
AgeGen lab guides are educational only. We do not provide medical diagnosis, prescribe brands, or recommend specific doses. Talk to a licensed clinician before changing your supplement or medication routine.
