Liver function test explained: values, meaning and procedure
A liver function test is a medical examination that provides important insights into the health of your liver. As a central organ of the body, the liver plays a crucial role in detoxification, nutrient storage, and the production of vital proteins. But how can you tell if your liver is functioning properly and is healthy? Liver function tests measure specific values such as enzymes and bilirubin to detect potential issues like liver diseases or metabolic disorders. In this blog, you will learn which values are analyzed in a liver function test, when such a test is useful, and how to prepare for it. The procedure and the meaning of the results are also clearly explained.
Table of Contents
- When is a liver function test used?
- Which values are measured in a liver function test?
- How are liver function test results interpreted?
- What are the symptoms of liver disease?
- How should I prepare for a liver function test?
- What to do in case of abnormal values?
- Summary
When is a liver function test used?
A liver function test is commonly performed when there is a suspicion of liver disease or to assess liver performance. Here are some typical situations in which such a test is used:
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Unclear symptoms: Complaints such as fatigue, nausea, yellowing of the skin (jaundice), dark urine, or light-colored stool can indicate liver problems.
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Monitoring chronic conditions: People with known liver diseases such as hepatitis, cirrhosis, or fatty liver use the test for monitoring disease progression.
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Medication use: Certain medications, such as painkillers or cholesterol-lowering drugs, can strain the liver. The test helps detect damage early.
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Alcohol consumption: Excessive alcohol use puts a strain on the liver, and a test can check for possible damage.
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Risk factors: Individuals with increased risk for liver disease – due to obesity, diabetes, or family history – often undergo regular liver function testing.
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Preventive health check: Sometimes the test is part of a general health screening.
A liver function test can reveal issues before serious symptoms develop, allowing for early treatment and the prevention of complications (MedlinePlus, 2023).
Which values are measured in a liver function test?
A variety of markers can be examined in relation to liver health. Each of these markers serves a specific function and helps detect potential problems early. Commonly measured values include:
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ALT (alanine aminotransferase): This enzyme is produced in the liver and indicates cell damage when levels are elevated.
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AST (aspartate aminotransferase): Also an enzyme, AST is found not only in the liver but also in other tissues, and is often assessed together with ALT.
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Bilirubin: As a breakdown product of hemoglobin, bilirubin shows how well the liver processes and excretes red blood cells.
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Gamma-GT (gamma-glutamyl transferase): This marker indicates disturbances in bile flow and is active in the liver and bile ducts.
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ALP (alkaline phosphatase): Elevated levels can indicate issues with the bile ducts or skeletal system.
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Albumin: This important protein is produced by the liver and is used to assess liver function and nutritional status.
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Prothrombin time (INR): It indicates how efficiently the liver regulates blood clotting and may be prolonged in liver disease.
Source: Mayo Clinic, 2025
How are liver function test results interpreted?
The following overview provides the normal ranges for key markers, common deviations, and their possible meanings. Note that reference values may vary slightly depending on the test laboratory, analysis methods, or individual factors. The unit U/L stands for “units per liter” and reflects the enzyme concentration in the blood.
| Marker | Normal range (reference value) | Deviation | Possible meaning |
|---|---|---|---|
| ALT (alanine aminotransferase) | 10–50 U/L | > 50 U/L | Indicates liver damage, e.g., from hepatitis, medication, or alcohol. |
| AST (aspartate aminotransferase) | 10–40 U/L | > 40 U/L | May indicate liver damage, muscle disease, or heart issues. |
| Bilirubin (total) | 0.1–1.2 mg/dL (1.7–20.5 µmol/L) | > 1.2 mg/dL (20.5 µmol/L) | May suggest jaundice, bile duct blockages, or hemolysis. |
| Gamma-GT (gamma-glutamyl transferase) | Men: 10–71 U/L | ||
| Women: 6–42 U/L | Men: > 71 U/L | ||
| Women: > 42 U/L | Suggests bile duct disorders, alcohol abuse, or liver inflammation. | ||
| Albumin | 35–55 g/L | < 35 g/L | May indicate cirrhosis, chronic illness, or malnutrition. |
| Prothrombin time (INR) | 0.8–1.2 | > 1.2 | Prolonged clotting time, suggesting impaired liver function. |
Source: Cleveland Clinic, 2022
What types of liver function tests are there?
Liver function tests often consist of a combination of different markers, assembled as needed to answer specific questions about liver health. Here are some commonly performed liver function tests:
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Comprehensive liver panel: This extensive test analyzes markers such as ALT, AST, ALP, bilirubin, and albumin to provide a complete picture of liver health. It is commonly used when liver disease is suspected or to monitor chronic conditions.
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Bilirubin test: This test focuses specifically on the bilirubin marker to diagnose jaundice, bile duct blockages, or issues with red blood cell breakdown.
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Enzyme tests (ALT and AST): These tests measure the concentration of ALT and AST enzymes and are used to detect liver cell damage from infections or medications.
What test methods are used for liver function tests?
There are different methods for conducting liver function tests, depending on the situation and personal preference:
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Blood draw at a doctor’s office or laboratory: This is the most common method. A small amount of blood is taken from a vein and analyzed in a lab for various markers.
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At-home tests: These allow you to perform liver function tests conveniently and anonymously at home. A finger prick provides a blood sample, which is sent to a certified lab. This option is ideal for those who wish to monitor their health regularly.
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Urine tests: Some liver problems can also be detected through urine, such as tests for bilirubin or urobilinogen. However, this method is less common than blood tests.
Source: MedlinePlus, 2023
Homed-IQ offers convenient at-home tests that allow you to easily and reliably check your liver health – without needing a doctor’s appointment. The Homed-IQ liver function test measures key markers such as ALT, AST, bilirubin, and gamma-GT to provide a comprehensive view of liver function. The results are analyzed in ISO-certified laboratories, which are also used by clinics and medical practices, ensuring the highest standards of quality and safety. Detailed instructions on how to perform the test are available on our YouTube channel.
What are the symptoms of liver disease?
Liver diseases can cause a variety of symptoms, which vary depending on the type and severity of the condition. These symptoms often appear nonspecifically at first but can become more noticeable as the disease progresses:
Common symptoms of liver disease
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Fatigue and weakness: A general feeling of exhaustion is often one of the first signs.
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Loss of appetite and weight loss: Liver problems can affect metabolism and appetite.
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Jaundice (icterus): Yellowing of the skin and eyes caused by increased bilirubin levels in the blood.
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Dark urine and pale stool: Changes in elimination are often a sign of issues with bilirubin metabolism.
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Abdominal pain and bloating: Pain in the upper right abdomen can indicate liver inflammation or enlargement.
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Itching (pruritus): Caused by the accumulation of bile salts in the skin.
Advanced symptoms
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Swelling in legs and abdomen (ascites): Fluid buildup is common with cirrhosis or advanced liver disease.
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Bleeding tendency and bruising: Due to reduced production of clotting factors by the liver.
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Confusion or memory problems: A sign of hepatic encephalopathy caused by toxin buildup in the blood.
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Spider angiomas (spider veins): Small, visible blood vessels under the skin.
Source: Cleveland Clinic, 2023
If one or more of these symptoms occur—especially jaundice, severe fatigue, or abdominal pain—a doctor should be consulted immediately. Early diagnosis can help prevent serious complications such as liver failure, bile duct blockages, or life-threatening infections.
How should I prepare for a liver function test?
To ensure accurate liver function test results, it may be important to avoid certain behaviors beforehand, such as alcohol consumption. For more detailed information, consult your doctor or the test provider.
What to do in case of abnormal values?
If abnormal values are detected, they should be discussed with a doctor. Only a medical professional can properly interpret the results in the context of your health and initiate further examinations or treatments if necessary.
Summary
A liver function test provides valuable insights into liver health by analyzing markers such as enzymes, bilirubin, and albumin. It is often used for unclear symptoms, to monitor diseases, or as part of routine health checks. The results help detect potential liver problems early and initiate appropriate measures if necessary. For reliable analysis of liver values, Homed-IQ offers practical at-home tests whose results are evaluated in certified laboratories.
