ALT blood test – a liver test that can show liver damage
ALT, alanine aminotransferase, is an enzyme that is primarily found in the cells of the liver. A smaller amount of ALT is also found in skeletal muscle and other tissues, among other things. The enzyme is involved in the body's metabolism of amino acids and energy production.
When liver cells are damaged or affected, ALT can leak into the blood. An ALT blood test is therefore used as a liver test to detect and monitor possible liver damage. Elevated ALT can occur in fatty liver, liver inflammation, certain infections or the effects of drugs and alcohol, among other things.
The test is often called P-ALT, which means that the enzyme activity is measured in blood plasma. An ALT test can be ordered separately or included together with other liver tests in a health check.
What does an ALT test show?
An ALT test shows the amount or activity of the enzyme ALT in the blood. Since ALT is mainly found in the liver, the test is used as a marker for the effect on liver cells.
An elevated ALT value may indicate that the liver is stressed, inflamed or damaged. However, the test alone cannot show what is causing the change or how well the liver is functioning. The result therefore usually needs to be assessed together with other liver values, symptoms, medications, alcohol habits and medical history.
A single abnormal ALT value does not automatically mean that you have a serious liver disease. In the event of an unexpected result, a new blood test after some time can show whether the change was temporary or persists.
Common causes of elevated ALT
A slightly elevated ALT value is relatively common. A mild or temporary increase does not have to be due to a serious illness and can occur for several different reasons.
- Medicines and dietary supplements: Some medications, herbal remedies, and dietary supplements can affect the liver and increase ALT levels.
- Alcohol: Regular or heavy alcohol consumption can contribute to elevated liver levels.
- Overweight and fatty liver: Fat accumulation in the liver is a common cause of mild or moderate elevated ALT.
- Hard physical activity: Intense exercise and muscle damage can sometimes cause a temporary increase in ALT.
- Infection or temporary illness: Some infections can affect liver levels for a limited period.
- Metabolic effects: Insulin resistance, type 2 diabetes, and elevated blood fats may be associated with fatty liver and elevated ALT.
If ALT is clearly elevated, continues to rise, or is above the reference range for a longer period of time, further medical investigation may be needed.
What can cause a long-term high ALT?
A long-term elevated ALT value can occur in several different conditions that affect the liver. The significance of the result depends on, among other things, how much the value is elevated, how long the change has been present, and whether other liver tests are also abnormal.
- Fatty liver: Fatty liver can be linked to obesity, insulin resistance, type 2 diabetes, high blood fats, and other metabolic risk factors.
- Liver inflammation: Examples include viral hepatitis, autoimmune hepatitis, and alcohol-related liver inflammation.
- Drug-induced liver damage: Certain medications and dietary supplements can cause irritation or damage to liver cells.
- Viral infections: Hepatitis B and hepatitis C are examples of infections that can cause elevated liver values.
- Metabolic or hereditary conditions: Some more unusual diseases can affect liver function and produce abnormal liver tests.
- Liver fibrosis or cirrhosis: Long-term liver damage can lead to scarring, but the ALT value alone cannot confirm or rule out this.
What is a normal ALT value?
The reference range for ALT varies between different laboratories and analysis methods. It can also differ depending on age and sometimes gender. The result is usually given in µkat/L.
You should always start from the reference range that is given together with your own test result. A value just above the range does not necessarily mean that you have a serious liver disease. Similarly, a value within the reference range alone cannot rule out all liver damage.
The ALT value should be interpreted taking into account previous test results, other liver tests, any symptoms, medication use and other risk factors. In the event of a deviation, repeated sampling or additional examinations may be recommended.
High P-ALT – what does an elevated liver value mean?
A high P-ALT means that the enzyme activity of ALT in the blood plasma is above the laboratory's reference interval. This often indicates that the liver cells are affected, but the test result itself does not show what the cause is. Elevated P-ALT can, for example, occur in fatty liver, liver inflammation, drug effects, certain infections or alcohol-related liver effects. Also a recent hard workout or muscle injury can in some cases affect the result.
A slight increase is common and may be temporary. A severely or long-term elevated ALT value, however, should be followed up with other liver tests and a medical assessment.
Slightly elevated ALT
A slightly elevated ALT can be seen in cases such as overweight, fatty liver, insulin resistance, medication use, alcohol consumption or after intense physical activity. In many cases, a new test is recommended after a certain time to see if the value has normalized or is still elevated.
Severely elevated ALT
A severely elevated ALT can occur with a more pronounced or acute impact on the liver cells. The result then needs to be assessed urgently based on other liver values, symptoms, medications and any underlying disease.
P-ALT low – is a low value dangerous?
A low P-ALT has no clinical significance in most cases and is usually considered normal. It does not normally require any treatment or special follow-up.
Low values can sometimes occur in people with low muscle mass, such as elderly or malnourished people. However, a low ALT value should not be used as sole evidence that the liver is completely healthy, since the health of the liver is assessed using several tests and other medical information.
The result usually only needs to be investigated further if other blood tests are abnormal or if there are symptoms that may indicate disease.
How is ALT interpreted together with other liver tests?
ALT is often analyzed together with other liver tests to provide a more comprehensive picture of the liver and biliary tract. The pattern between different test values can provide information about the type of impact that may be present.
ALT and AST
ALT and AST can both rise when liver cells are affected. AST is also found in, among other things, the heart and skeletal muscle and is therefore less specific for the liver than ALT. The ratio between ASAT and ALAT can provide some guidance, but cannot alone determine the cause of elevated values.
ALAT and ALP
ALP, alkaline phosphatase, is linked to the bile ducts, among other things, but is also found in the skeleton. If both ALAT and ALP are elevated, there may be reason to examine the liver and bile ducts more closely.
ALAT and GT
GT, gamma-glutamyltransferase, can increase due to, among other things, alcohol exposure, fatty liver, certain medications and effects on the bile ducts. An elevated GT value is not specific to alcohol and needs to be assessed together with ALAT and other test results.
ALAT and bilirubin
Bilirubin is formed when red blood cells are broken down and then processed by the liver. Elevated bilirubin can occur, among other things, in cases of liver damage, increased breakdown of red blood cells or obstruction of bile flow.
Albumin and PK(INR)
Albumin and PK(INR) can be used in certain situations to assess the liver's ability to form proteins and coagulation factors. These tests provide different information than ALT, which primarily shows possible effects on liver cells.
When may it be relevant to test ALT?
A blood test for ALT may be relevant as part of a health check, when following up on previously abnormal liver values or when there are risk factors for liver damage. For example, it may be appropriate to check ALT in the following cases:
- overweight or suspected fatty liver
- type 2 diabetes or insulin resistance
- regular or extensive alcohol intake
- treatment with medications that can affect the liver
- previously elevated liver values
- suspected or previously diagnosed liver disease
- follow-up of lifestyle changes or medical treatment
Symptoms that may occur when the liver is affected
Many liver diseases do not cause clear symptoms in the early stages. An ALT blood test can therefore provide information even before clear symptoms have arisen. The following symptoms may sometimes occur when the liver or biliary tract is affected:
- persistent fatigue or weakness
- nausea or decreased appetite
- discomfort or pain in the upper abdomen
- pain or discomfort under the right rib cage
- yellow skin or the whites of the eyes
- dark-colored urine
- unusually light-colored stools
- unexplained itching
- unexplained weight loss
These symptoms are not specific to liver disease and can have many other causes. An ALT test can provide information but is not a substitute for a medical evaluation.
How an ALT blood test is done
ALT is measured through a regular blood sample taken from a vein in the arm. The test usually only takes a few minutes. ALT can be ordered as a single blood sample or r be included in a larger liver test together with, for example, ASAT, ALP, GT and bilirubin.
Always follow the instructions before the test. If necessary, inform about which medications and dietary supplements you are using. It may also be relevant to take into account recent hard training as this can sometimes affect the test result.
Do you need to fast before an ALT blood test?
A single ALT test usually does not require fasting. If ALT is part of a larger health check, other analyses in the same test may require you to be fasting. Therefore, always follow the instructions that belong to the test or health check you have ordered.
Order a blood test for ALT
By testing ALT, you will get information about one of the most common liver values. The test can be used to detect possible liver damage, follow up on a previous abnormal result or as part of a broader liver health check.
After ordering the test, you will submit a blood sample to an affiliated testing clinic. When the analysis is complete, the result will be available digitally along with the laboratory's reference range.
When should you contact healthcare?
Contact healthcare if you have recurring or prolonged elevated liver values, persistent symptoms or other signs of possible liver damage. Seek medical attention urgently if you develop yellow skin or the whites of your eyes, especially if you also have fever, chills, severe abdominal pain, repeated vomiting, confusion or a clearly worsening general condition.
