Liver Function Tests (AST, ALT, ALP, GGT)
Definition
A group of tests that evaluate liver health. Main components:
| Component | What it is | What an elevation means |
|---|---|---|
| ALT (Alanine Aminotransferase) | An enzyme produced mainly in the liver | Liver inflammation or damage |
| AST (Aspartate Aminotransferase) | An enzyme produced mainly in the liver | Liver inflammation, hepatitis |
| ALP (Alkaline Phosphatase) | An enzyme produced mainly in the liver | Bone disease or liver disease, additional testing is needed to distinguish between the two |
| GGT (Gamma-Glutamyl Transferase) | An enzyme produced mainly in the liver | Liver problems |
| Albumin | A protein produced in the liver | If low, liver dysfunction |
| Bilirubin | A waste product formed from the breakdown of old red blood cells; cleared by the liver | Jaundice, decline in liver function |
Purpose
To investigate whether symptoms result from liver disease or damage, to monitor an existing condition, and to check for medication side effects.
Results
Enzyme elevations suggest liver cell damage or a bile flow problem; however, which enzyme is elevated, by how much, and their ratio to one another matters.
Normal Values
Laboratory-specific, see the reference range on your report.
Risks and Limitations
Liver function tests alone usually cannot diagnose a specific disease, additional testing is needed for a definitive diagnosis. In particular, an elevated ALP can also originate from bone rather than the liver.