Liver function test results: ALT, AST, ALP, GGT, bilirubin and albumin
Liver function tests, also called a liver panel, measure several substances in one blood sample. Many of them are part of the comprehensive metabolic panel often ordered at a routine checkup. They can show whether the liver may be inflamed or damaged, but on their own they usually cannot name a specific disease. (MedlinePlus, liver tests)
What each test measures
The ACG says these should be called "liver chemistries" or "liver tests". (ACG, 2017)
| Test | What it is |
|---|---|
| ALT (alanine transaminase) | An enzyme made mainly in the liver. Raised ALT is more specific to the liver than AST, because ALT is found in only low amounts outside it. (MedlinePlus, liver tests) (BSG, 2018) |
| AST (aspartate aminotransferase) | An enzyme made mainly in the liver, but also found in large amounts in muscle, including the heart. (MedlinePlus, liver tests) (BSG, 2018) |
| ALP (alkaline phosphatase) | An enzyme found mostly in the liver, bile ducts and bone. (MedlinePlus, ALP range) (MedlinePlus, liver tests) |
| GGT (gamma-glutamyl transferase) | A liver enzyme that is not found in bone, so it helps show whether a high ALP comes from the liver or from bone. (MedlinePlus, GGT test) (BSG, 2018) |
| Bilirubin | A yellowish waste product made when old red blood cells break down. The liver removes most of it. (MedlinePlus, liver tests) (MedlinePlus, bilirubin test) |
| Albumin | The main protein made by the liver. It is often used as a sign of how well the liver makes proteins, but many other conditions lower it too. (MedlinePlus, liver tests) (BSG, 2018) |
The test is a blood sample from a vein in your arm. You will probably need to fast for 10 to 12 hours, and your provider will tell you how to prepare. (MedlinePlus, liver tests) See fasting before a blood test.
Typical adult ranges
These are the ranges MedlinePlus lists. Ranges vary slightly between labs, so the range printed on your report is the one that applies to you. (MedlinePlus, ALT range)(MedlinePlus, bilirubin range)
| Test | Typical adult range |
|---|---|
| ALT | 4 to 36 U/L (MedlinePlus, ALT range) |
| AST | 8 to 33 U/L (MedlinePlus, AST range) |
| ALP | 40 to 129 IU/L (MedlinePlus, ALP range) |
| GGT | 5 to 40 U/L (MedlinePlus, GGT range) |
| Total bilirubin | 0.1 to 1.2 mg/dL (1.71 to 20.5 micromol/L) (MedlinePlus, bilirubin range) |
| Direct (conjugated) bilirubin | less than 0.3 mg/dL (less than 5.1 micromol/L) (MedlinePlus, bilirubin range) |
| Albumin | 3.4 to 5.4 g/dL (34 to 54 g/L) (MedlinePlus, albumin range) |
The same ALT, AST, ALP, bilirubin and albumin ranges appear on the metabolic panel results page with the rest of the CMP.
The patterns doctors look for
If any result is abnormal, your provider compares all of them to look for patterns that suggest different kinds of liver problems. (MedlinePlus, liver tests)
- Mostly ALT and AST raised: the ACG calls this a hepatocellular pattern, meaning injury to the liver cells. (ACG, 2017)
- Mostly ALP raised: the ACG calls this a cholestatic pattern, meaning a problem with the flow of bile. (ACG, 2017) A high ALP with a high GGT points to the liver; a high ALP with a normal GGT points more to bone. (MedlinePlus, GGT test)
- Only bilirubin raised: the BSG guideline says the most common cause is Gilbert syndrome, an inherited condition that is not linked to liver disease. (BSG, 2018) A raised direct (conjugated) bilirubin points instead to liver disease or a blocked bile duct in most settings. (ACG, 2017)
How high a result is does not always tell how serious it is. The BSG guideline says this depends on which test is abnormal and on your health overall, and that people with liver scarring can have normal liver enzymes. (BSG, 2018)
Common reasons for a mild rise that is not liver disease
Abnormal results do not always mean a liver problem. (MedlinePlus, liver tests) The sources list these general reasons, which are possibilities for your doctor to look into, not a diagnosis.
- A recent illness: some abnormal results are temporary, and your provider may repeat the tests later. (MedlinePlus, liver tests)
- Exercise and muscle: intense exercise can affect ALT, (MedlinePlus, ALT test) strenuous exercise can raise bilirubin, (MedlinePlus, bilirubin test) and AST can rise with muscle or heart muscle damage. (BSG, 2018)
- Bone: ALP can come from bone disease as well as the liver. (MedlinePlus, liver tests) The BSG guideline says a raised ALP on its own may come from low vitamin D, or from normal growth in children. (BSG, 2018)
- Pregnancy: ALP is often higher and albumin lower in pregnancy without a liver problem, although other changes in pregnancy need prompt checking. (BSG, 2018)
- Gilbert syndrome: a common, harmless cause of a mildly raised bilirubin. (BSG, 2018)
- Other factors: age, sex, weight, the menstrual cycle, certain medicines and dietary supplements can affect ALT. (MedlinePlus, ALT test) GGT can be raised by alcohol, smoking and some medicines, and goes down after meals. (MedlinePlus, GGT test)
Among liver causes, fatty liver disease, alcohol-related liver disease and hepatitis C often show only mild or moderate rises. (BSG, 2018) For how fatty liver scarring is checked, see fatty liver screening and FIB-4.
What follow-up tests may come next
If your results are abnormal, you will usually need other tests to find the cause. (MedlinePlus, liver tests) In general terms, the guidelines describe:
- A review first: the BSG guideline says results should be read alongside your earlier results, medical history and current health. (BSG, 2018)
- Blood tests for the cause: for raised ALT and AST, the ACG lists tests for hepatitis A, B and C, a check for fatty liver and alcohol-related liver disease, and tests for hemochromatosis, autoimmune hepatitis, Wilson disease and alpha-1 antitrypsin deficiency, plus a review of prescribed and over-the-counter medicines. (ACG, 2017) See hepatitis B test results, hepatitis C test results and iron test results.
- For a raised ALP from the liver: the ACG lists tests for primary biliary cholangitis and primary sclerosing cholangitis, two conditions of the bile ducts. (ACG, 2017)
- For a raised bilirubin: splitting it into direct and indirect parts. (ACG, 2017)
- Imaging: the BSG standard set of tests for adults includes an abdominal ultrasound with the blood tests. (BSG, 2018)
- Biopsy: the ACG says a liver biopsy may be considered when blood tests and imaging do not give a diagnosis, to stage a condition, or when several diagnoses are possible. (ACG, 2017)
The BSG guideline says unexplained jaundice (yellow skin or eyes) or a suspected cancer of the liver or bile ducts should lead to an immediate referral. (BSG, 2018)
Where they differ:
- What counts as a normal ALT: MedlinePlus lists the usual lab range of 4 to 36 U/L, (MedlinePlus, ALT range) while the ACG and the AASLD say a truly healthy ALT is about 29 to 33 U/L in men and 19 to 25 U/L in women, and the AASLD treats ALT above 30 U/L as generally abnormal. (ACG, 2017) (AASLD, 2023)
- Repeat or look for a cause: MedlinePlus says your provider may repeat the tests after a recent illness, (MedlinePlus, liver tests) while the BSG guideline advises looking for the cause of any abnormal result, whatever its size or how long it has lasted, and repeating only when a short-term cause is likely. (BSG, 2018)
- Which tests make up the panel: the ACG names ALT, AST, ALP and bilirubin as the most common, (ACG, 2017) while the BSG starting set is bilirubin, albumin, ALT, ALP and GGT, with a full blood count. (BSG, 2018)
Your doctor decides what your result means for you.
This page does not give medicine, diet, alcohol or treatment advice. If you have a flagged result, see after an abnormal screening result for questions to ask.
Questions people ask
What is a normal ALT level?
MedlinePlus lists 4 to 36 U/L, and ranges vary slightly between labs. The ACG and the AASLD say a truly healthy ALT is lower, about 29 to 33 U/L in men and 19 to 25 U/L in women. Use the range printed on your own report and ask your doctor what yours means. (MedlinePlus, ALT range) (ACG, 2017) (AASLD, 2023)
Can exercise raise liver test results?
Yes. MedlinePlus says intense exercise can affect ALT, and strenuous exercise can raise bilirubin. AST is also found in muscle, so a muscle injury can raise it. (MedlinePlus, ALT test) (MedlinePlus, bilirubin test) (BSG, 2018)
What is Gilbert syndrome?
An inherited condition in which the liver does not process bilirubin normally. The BSG guideline says it is the most common cause of a raised bilirubin when the other liver tests are normal, affects 5 to 8% of people, and is not linked to liver disease or ill health. (BSG, 2018)
Should abnormal liver tests just be repeated?
MedlinePlus says that if you were ill recently, your provider may repeat the tests later. The BSG guideline found that most abnormal results were still abnormal a month later, so it advises looking for the cause rather than only repeating the same tests, unless a short-term cause is likely. (MedlinePlus, liver tests) (BSG, 2018)
Do I need to fast for liver function tests?
MedlinePlus says you will probably need to fast for 10 to 12 hours, and your provider will tell you how to prepare. Tell your provider about all medicines and supplements you take, but do not stop any unless your provider tells you to. (MedlinePlus, liver tests)