Check What Your Liver Numbers (AST, ALT, GGT) Mean

What does a liver function test look at?

The national health portal describes it as a group of tests used to diagnose liver and biliary diseases and to assess their severity and course. Blood is usually drawn from a vein on the inside of the elbow. The items are divided by what they do.

• Items reflecting damage to liver cells or bile ducts: ALT, AST, alkaline phosphatase (ALP), lactate dehydrogenase (LD), gamma-glutamyl transferase (GGT)
• Items reflecting the liver's metabolic and secretory function: bilirubin, ammonia, cholesterol
• Items reflecting the liver's synthetic function: total protein, albumin, prothrombin time

Among these, AST, ALT, and GGT are included as blood test items in the National Health Insurance Service's common general health checkup tests.

What are AST, ALT, and GGT?

The numbers below are the reference ranges given in the KDCA National Health Information Portal's liver function test guide (updated 2026).

The same guide explains that when liver cells are damaged, AST and ALT leak into the blood and their levels rise. It says that early in acute damage AST rises more than ALT, and after 24 to 48 hours ALT becomes higher. It explains that GGT rises more in obstructive liver diseases than in liver cell damage.

The reference ranges above are example values the portal gives. The portal says reference ranges differ slightly from lab to lab, so read your own results against the range printed on them.

Why can't you judge by the numbers alone?

The national health portal says a liver function test provides only indirect evidence of liver and biliary disease and is not used as a tool to diagnose a specific disease. There are two reasons.

• Individual values can change because of problems in the muscles, pancreas, or heart, not just the liver.
• When types of disease are close, the pattern of results looks similar too, so this test alone makes it hard to tell the cause. The portal says results must be interpreted together with other blood tests, imaging findings, and clinical information.

GGT can also rise with alcohol dependence, obesity, and the use of some medications, in addition to liver disease. If your result is above the reference range, bring a summary of your recent lifestyle and medications to your consultation.

Is there anything to prepare before the test?

The portal's liver function test guide (updated 2026) says most items need no special preparation. If items affected by meals, such as cholesterol, are included, blood is drawn after fasting for 9 to 12 hours. For a general health checkup, follow the fasting instructions from the screening institution.

What should you check when you get your results?

When you open your results, go through the four items below in order.

• The value for each item and the reference range marked on your results
• Whether the item above the range is AST, ALT, or GGT
• How the same item looked in your previous checkup
• The medications you have taken recently and any conditions you have

When should you contact a medical institution?

If your results are marked for retesting or consultation, talk to a medical institution. The national health portal describes jaundice or darker urine, fatigue and loss of appetite, abdominal pain or swelling, and nausea or vomiting as findings that raise suspicion of liver disease. If you have symptoms like these, contact a doctor regardless of your checkup results. Don't decide the cause or treatment on your own from the numbers. Confirm it through a medical visit.