What Elevated Liver Enzymes May Indicate: ALT, AST, GGT, ALP
The short answer
Elevated liver enzymes show that liver cells or bile ducts are under stress, but not why. The pattern narrows it down. ALT and AST leading suggests liver cell injury. ALP and GGT leading suggests a bile flow problem.
The most common causes are fatty liver disease, alcohol, and medicines or supplements. Any result above the laboratory's interval needs medical review.
What each liver marker reflects
The panel usually called liver function tests mostly measures injury, not function. Each marker has a different source.
| Marker | Main source | Worth knowing |
|---|---|---|
| ALT | Liver cells | The most liver-specific of the enzymes |
| AST | Liver cells, muscle, heart, red cells | Rises after hard exercise or muscle injury as well as liver injury |
| GGT | Bile ducts and liver | Sensitive but not specific. Raised by alcohol, some medications and fatty liver. |
| ALP | Bile ducts and bone | Also raised in pregnancy and in growing adolescents |
| Bilirubin | Breakdown of red cells | Splitting it into conjugated and unconjugated shows where the problem sits |
| Albumin | Made by the liver | A true function marker. It changes slowly and also falls with inflammation. |
The patterns
The American College of Gastroenterology guideline sorts abnormal results by which enzymes are raised out of proportion to the others (Kwo et al., 2017).
- Hepatocellular. ALT and AST are raised out of proportion to ALP. This points to injury of the liver cells.
- Cholestatic. ALP is raised out of proportion to ALT and AST, usually with GGT. This points to impaired bile flow.
- Mixed. Both groups are raised.
Four further clues help:
- ALP raised with normal GGT suggests the ALP is coming from bone, not liver.
- GGT raised alone is common with alcohol, some medications and fatty liver.
- AST well above ALT is a recognised feature of alcohol-related liver disease. AST raised alone after hard training may be muscle, not liver.
- Raised conjugated bilirubin implies liver cell disease or bile duct obstruction in most settings.
Common causes, and a note on upper limits
The guideline's work-up for a hepatocellular pattern covers the causes below. Fatty liver disease and alcohol account for most cases seen in the community.
- Fatty liver disease linked to metabolic health
- Alcohol
- Prescribed and over-the-counter medicines
- Viral hepatitis A, B and C
- Hereditary haemochromatosis
- Autoimmune hepatitis
- Rarer inherited conditions, including Wilson disease and alpha-1 antitrypsin deficiency
Herbs and supplements belong on the list. Herbal and dietary supplements are a recognised cause of liver injury. Record everything the client takes, including what you have prescribed, and pass that list to the GP when you refer.
Upper limits are debated. The same guideline states that a true healthy normal ALT is 29 to 33 IU/L for men and 19 to 25 IU/L for women, and that levels above this should be assessed. Many laboratory upper limits sit higher. An ALT inside the printed interval but above these figures, especially with raised triglycerides or GGT, is worth following over time. See conventional vs functional reference ranges.
When to refer, and where a platform helps
Liver enzyme changes are a medical question first.
- Any liver marker above the laboratory's interval: refer to the client's GP, with a full list of medicines, herbs and supplements.
- Jaundice, dark urine, pale stools, abdominal pain or confusion: same-day medical care.
- Results in range but rising across tests: retest under the same conditions and tell the GP if the trend continues.
- A new rise after starting a herb or supplement: stop and refer. Do not wait for a second result.
Seeing the pattern means reading six markers against each other and against earlier results. Beyond Normal shows liver markers against conventional and functional intervals in Australian units, calculates ratios and charts each marker across visits, so a slow rise inside the range is visible. To compare tools, see the best online platforms for practitioners to interpret blood tests.
Related reading: how to identify patterns across blood markers and how to track pathology changes over time.
Frequently asked questions
What do elevated liver enzymes mean?
They mean liver cells or bile ducts are under stress. The cause can be fatty liver disease, alcohol, medicines or supplements, viral hepatitis or less common conditions. The pattern of which enzymes are raised helps narrow it down.
What is the difference between ALT and AST?
ALT comes mostly from the liver. AST also comes from muscle, heart and red cells, so it can rise after hard exercise or muscle injury.
What does a raised GGT on its own mean?
An isolated raised GGT is common with alcohol, some medications and fatty liver. It is sensitive but not specific, so it needs to be read with the other liver markers and the history.
What does a raised ALP mean?
ALP comes from bile ducts and bone. If GGT is also raised, the source is likely the liver. If GGT is normal, bone is more likely.
Can herbs and supplements raise liver enzymes?
Yes. Herbal and dietary supplements are a recognised cause of liver injury. A new rise in liver enzymes after starting a product is a reason to stop it and seek medical review.
What is a normal ALT level?
Laboratory intervals vary. The American College of Gastroenterology states that a true healthy normal ALT is 29 to 33 IU/L for men and 19 to 25 IU/L for women.
Sources
Journal citations were checked against PubMed on 4 October 2026.
- Kwo PY, Cohen SM, Lim JK. ACG Clinical Guideline: Evaluation of abnormal liver chemistries. Am J Gastroenterol. 2017;112(1):18-35. doi:10.1038/ajg.2016.517
- Newsome PN, Cramb R, Davison SM, et al. Guidelines on the management of abnormal liver blood tests. Gut. 2018;67(1):6-19. doi:10.1136/gutjnl-2017-314924
