Understanding Liver Function Tests: What Your Numbers Mean

If your doctor has ever ordered bloodwork, there's a good chance a liver panel was included. These tests are common, but the abbreviations and reference ranges on the results page can be confusing. Here's a plain-English breakdown.

What Is a Liver Panel?

A liver panel (also called a liver function test or LFT) is a group of blood tests that measure enzymes, proteins, and substances the liver produces or processes. On their own, individual markers don't tell the whole story — doctors typically look at the full pattern.

ALT (Alanine Aminotransferase)

ALT is an enzyme found mostly in liver cells. When liver cells are damaged, ALT leaks into the bloodstream, so elevated levels often point toward liver cell stress or injury.

AST (Aspartate Aminotransferase)

AST is similar to ALT but is also found in muscle and heart tissue, so it's less specific to the liver on its own. Doctors often compare the AST-to-ALT ratio for additional context.

ALP (Alkaline Phosphatase)

ALP is linked to the bile ducts. Elevated levels can suggest a blockage or issue with bile flow, though ALP is also produced in bone, so context matters here too.

Bilirubin

Bilirubin is a byproduct of red blood cell breakdown that the liver processes and excretes. Elevated bilirubin is what causes jaundice (yellowing of skin and eyes) and can point to a liver or bile duct issue.

Albumin

Albumin is a protein made by the liver. Since a healthy liver is needed to produce it, low albumin levels can be a sign of reduced liver function, especially in more advanced cases.

GGT (Gamma-Glutamyl Transferase)

GGT is often used alongside ALP to help pinpoint whether an elevated ALP is related to the liver or to bone. It's also sensitive to alcohol intake.

What Counts as "Normal"?

Reference ranges vary somewhat by lab, but they're typically printed right next to your result on the lab report. A single mildly elevated number isn't necessarily a red flag — labs can fluctuate with recent exercise, alcohol, or even certain medications. Trends over time and the overall pattern matter more than any one number in isolation.

When to Talk to Your Doctor

If your results come back outside the reference range, your doctor is the best person to interpret them in the context of your health history, medications, and any symptoms you're experiencing. Repeat testing is common before further steps are recommended.