Liver function tests are blood tests that measure different substances produced by your liver. These measurements give your healthcare provider important information about the overall health of your liver and how well it's working. A liver panel will often measure several substances in one blood sample.
What are the five primary liver function tests?
The most common liver tests include:
- Liver enzymes test. Your liver enzymes include alkaline phosphatase (ALP), alanine transaminase (ALT), aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT). These are elevated when there’s liver injury.
- Total protein test.A total protein test measures levels of protein in your blood. Your liver makes protein, and low protein levels may indicate that your liver isn’t functioning optimally.
- Bilirubin test. Bilirubin is a waste product that your liver deposits in bile.
- LDH test. Lactate dehydrogenase (LDH) is an enzyme found in many of your body’s tissues, including your liver.
- Prothrombin Time (PT) test. This test measures how long it takes for a sample of your blood to clot, a process that involves proteins that your liver produces.
These tests are all part of a routine blood panel called a comprehensive metabolic panel.
When are tests done to check liver function?
Your healthcare provider might want to check these values to screen you for possible hepatitis or other liver diseases. If they already know that you have liver disease, they might want to check how it’s progressing or whether a treatment is working. You may also have a liver test to monitor the side effects of certain medications that are known to affect your liver.
How do liver function tests work?
A healthcare provider draws a small amount of blood from a vein in your arm to test in the lab. They’ll look for abnormally high or low levels of different substances. Often, they’ll want to compare levels of different enzymes or proteins to each other. If the balance is off, that can help them understand better what may be going on in your liver.
What is the normal range for liver function tests?
Normal ranges vary between different sexes and body sizes, as well as between different laboratories. On average, normal ranges are:
- Alanine transaminase (ALT): 0 to 45 IU/L.
- Aspartate transaminase (AST): 0 to 35 IU/L.
- Alkaline phosphatase (ALP): 30 to 120 IU/L.
- Gamma-glutamyltransferase (GGT): 0 to 30 IU/L.
- Bilirubin: 2 to 17 micromoles/L.
- Prothrombin time (PT): 10.9 to 12.5 seconds.
- Albumin: 40 to 60 g/L.
- Total proteins: 3 to 8.0 g/dL.
