Finding a raised ALT, AST, GGT, ALP or bilirubin on a blood test is a common situation. These results do not always mean there is serious liver disease. But if the elevation persists, the reason for it should be looked into.
What are the liver tests?
Each of the tests commonly called “liver enzymes” or “liver function tests” tells you about something different.
ALT (alanine aminotransferase): Found in high concentrations in liver cells. A raised ALT usually suggests damage to or irritation of the liver cells.
AST (aspartate aminotransferase): Also found in muscle and other tissues outside the liver. A raised AST is therefore not always coming from the liver.
GGT (gamma-glutamyl transferase): Can rise in bile duct disease, with certain medicines and with alcohol. A raised GGT on its own does not establish any particular diagnosis.
ALP (alkaline phosphatase): Can rise particularly where the bile ducts are obstructed or bile flow is disturbed. But it can also rise for reasons outside the liver, such as bone disease.
Bilirubin: A substance produced when red blood cells break down, which the liver then processes. When bilirubin rises, the whites of the eyes and the skin can turn yellow.
Albumin and clotting tests (INR): Tell you about the liver’s capacity to make proteins. They matter particularly in assessing chronic or advanced liver disease.
Why do liver tests become abnormal?
Abnormal liver tests can have a great many causes. Among the common ones are:
- Fatty liver arising from metabolic causes
- Alcohol use
- Viral hepatitis such as hepatitis B and hepatitis C
- Medicines and certain herbal products or supplements
- Gallstones and obstruction of the bile ducts
- Autoimmune liver disease
- Certain diseases involving the accumulation of iron or copper
- Muscle disease or intense exercise
- Rarer inherited and metabolic diseases
Does a high value always mean serious disease?
No.
Liver enzymes can rise slightly and temporarily. Some values may go up for a while after an infection, a medicine or a bout of intense exercise, for example.
On the other hand, tests that stay high for a long time, values that are markedly raised, or the presence of other abnormal findings alongside them call for a more detailed assessment.
What matters is not simply that a value is “high”: it is which test is raised and by how much, how it relates to the other tests, and how long the situation has been going on.
Does it matter if I have no symptoms?
Yes, it can.
Some liver diseases can progress for many years without producing any symptom at all. Fatty liver and chronic viral hepatitis are important examples.
Feeling well does not therefore mean that abnormal liver tests need not be investigated.
What investigations might your doctor request?
Not every patient needs the same tests. The first things assessed are the medicines and supplements being taken, alcohol use, weight and metabolic disease, past illnesses and family history.
Where it is thought necessary, the following may be requested:
- Repeat measurement of ALT, AST, GGT, ALP and bilirubin
- A full blood count and other biochemical tests
- Hepatitis B and C tests
- Tests relating to iron metabolism
- Investigations for autoimmune liver disease
- Liver ultrasound
- Elastography methods that assess fat and stiffness in the liver
- MRI, MRCP or other advanced imaging
Some patients need further investigation, and rarely a liver biopsy.
When should it be assessed sooner?
If abnormal liver tests are accompanied by yellowing of the eyes or skin, markedly darker urine, paler stools, severe abdominal pain, fever, persistent vomiting, altered consciousness or a marked deterioration in general condition, medical assessment should not be delayed.
My liver tests came back high — what should I do?
The first thing is not to panic. A single blood test is often not enough to reach a definite diagnosis.
But nor is it right for someone to diagnose themselves by looking the results up on the internet or comparing them against reference ranges. The pattern and the cause of abnormal liver tests need to be assessed by a doctor, together with the person’s history, the medicines they take, the examination findings and, where necessary, imaging.
Where the tests are found to be high on repeated measurement, where they are markedly raised, or where there are other findings such as a raised bilirubin, a gastroenterology assessment would be appropriate.
Remember: an abnormality in the liver tests is not the name of a disease. It is a finding that needs to be investigated. The right approach is to establish which test is abnormal and why.
Sources
- Prof. Ali Tüzün İnce, MD