Common Liver Tests: Understanding Liver Function Assessment

Comprehensive overview of common liver tests, their roles in diagnosing liver health, and what the results can mean.

By Sneha Tete, Integrated MA, Certified Relationship Coach

Created on Oct 3, 2025

Comprehensive overview of common liver tests, their roles in diagnosing liver health, and what the results can mean.

The liver, one of the body’s most vital organs, performs numerous critical functions, including filtering blood, metabolizing nutrients, and aiding in digestion. When there is concern about liver health, physicians turn to a range of blood tests, commonly referred to as liver function tests (LFTs), to assess the state and performance of the liver. This article reviews the principal tests used to evaluate liver function, what each measures, and how these results guide medical care.

What Are Liver Function Tests?

Liver function tests, often called a liver panel, comprise a group of blood tests designed to gauge different markers associated with liver metabolism and injury. These tests help:

Detect inflammation or damage in liver tissue
Monitor the progression of liver diseases
Guide treatment decisions
Screen for complications, such as issues with bile flow or clotting

Liver function tests can suggest but not directly diagnose the cause of liver injury, and they are often used alongside other clinical evaluations, imaging, and sometimes biopsies.

Why Are Liver Tests Ordered?

Physicians may recommend liver tests for several reasons:

To investigate symptoms of liver disease (e.g., jaundice, fatigue, pain in the upper right abdomen)
To monitor known liver conditions or the effects of medications that could impair liver function
To screen individuals at higher risk (e.g., those with hepatitis, heavy alcohol use, or metabolic disorders)

Because the liver’s health impacts various body processes, even routine health exams may include basic liver function tests.

Types of Common Liver Tests

The most widely used liver tests can be broadly categorized by what they measure: enzymes, proteins, and waste products.

Enzyme Tests

Alanine transaminase (ALT): ALT is an enzyme primarily found in the liver. Raised ALT levels often indicate acute liver cell injury or inflammation, and the test is valuable in monitoring conditions like hepatitis.
Aspartate transaminase (AST): AST is found in multiple tissues, but high blood levels commonly signal liver or muscle damage. Ratios of ALT to AST help differentiate causes of liver problems.
Alkaline phosphatase (ALP): Found most abundantly in the liver, biliary tract, and bone. Elevated ALP can point to bile duct blockages, gallstones, or bone disorders. In liver tests, high ALP generally suggests issues affecting bile flow.
Gamma-glutamyl transpeptidase (GGT): GGT is produced in the liver and biliary tract. Elevated GGT is useful in confirming the hepatic origin of raised ALP, and it is sensitive in detecting excessive alcohol use and other biliary conditions.
Lactate dehydrogenase (LDH): This enzyme exists throughout the body and increases in instances of tissue damage, such as from injury or certain diseases. However, LDH is not specific to the liver and is less commonly used alone for liver diagnostics.
5′-Nucleotidase: Made specifically by the liver, this enzyme’s levels are high in cholestatic liver diseases (conditions that disrupt bile flow). Elevated 5′-nucleotidase helps confirm liver rather than bone as the source of abnormal ALP values.

Protein and Clotting Factor Tests

Serum Albumin: Albumin, the major blood protein made by the liver, maintains blood volume and transports substances. Low albumin may indicate chronic liver disease or reduced synthetic capacity.
Total Protein: Measures the cumulative levels of all proteins (mostly albumin and globulins) produced in the liver. Deviations can suggest a variety of conditions, including liver dysfunction or immune disorders.
Prothrombin Time (PT) and International Normalized Ratio (INR): The liver produces proteins essential for blood clotting. PT and INR assess how quickly blood clots, with prolonged times hinting at liver impairment or vitamin K deficiency. INR is now the standard reporting parameter, allowing comparison across labs.

Waste Product Tests

Serum Bilirubin: Bilirubin is a yellow pigment made from the breakdown of red blood cells. The liver processes and excretes bilirubin through bile. Elevated bilirubin in blood causes jaundice and may occur from liver dysfunction, bile duct obstruction, or excessive red cell breakdown.

Clinical Interpretation of Liver Tests

While each test provides valuable information, the pattern of abnormalities is often more informative than any single result. Here is a table summarizing the main markers and what they may indicate:

Test	What It Measures	What High Levels May Indicate
ALT	Enzyme from liver cells	Liver cell injury (e.g., hepatitis, medication side effects)
AST	Enzyme from liver and other tissues	Liver cell injury, muscle injury, heart disease
ALP	Enzyme from liver, bile ducts, bone	Bile duct obstruction, bone disease, liver tumors
GGT	Enzyme from liver, biliary tract	Biliary tract disease, alcohol overuse, certain drugs
LDH	Enzyme from many body tissues	General tissue damage, not specific for liver
5′-Nucleotidase	Enzyme made in liver	Cholestasis, bile flow disorders
Albumin	Protein made by liver	Low: chronic liver disease, kidney disease, malnutrition
PT / INR	Blood clotting proteins made by liver	Prolonged time: liver dysfunction, vitamin K deficiency
Bilirubin	Pigment excreted in bile	Liver damage, bile duct problems, excessive hemolysis

What Do Abnormal Liver Test Results Mean?

Interpreting liver tests requires a careful assessment of the entire clinical picture. Possible scenarios include:

Pattern of damage: Predominantly elevated ALT and AST suggest hepatitis or direct liver cell injury. Marked elevations in ALP and GGT hint at cholestasis or bile duct obstruction.
Severity: The height of the elevations often correlates with the degree but not always the cause of injury.
Chronic vs. acute: Albumin and INR are usually affected in chronic, advanced disease rather than early, acute injury.
Non-liver sources: AST and ALP are also found in other organs, so test results sometimes reflect issues outside the liver.

Further testing, such as imaging (ultrasound, CT), specialized bloodwork, or even liver biopsy may be warranted for diagnosis and management.

Other Diagnostic Procedures

Blood tests alone may not offer a complete diagnosis. When unusual results or persistent symptoms occur, additional tests may include:

Ultrasound, CT, or MRI: Imaging tests detect structural abnormalities such as tumors, cysts, or blockages.
Liver Biopsy: Involves removing a small tissue sample for microscopic examination. Types include:

Percutaneous: Needle through the skin into the liver
Laparoscopic: Small abdominal incision using camera guidance
Transvenous: Via catheter in large neck vein (for patients with bleeding risk)

Biopsy is reserved for when the diagnosis is unclear, or when grading the severity of disease (such as fibrosis or cirrhosis) is necessary.

Special Considerations in Liver Function Testing

Medications and Alcohol: Many prescription drugs, over-the-counter medications, and herbal supplements can influence liver enzyme results. Alcohol commonly elevates GGT and, in heavy use, other enzymes.
Transient Elevations: Minor, short-lived abnormalities may simply reflect temporary stress or minor insults to the liver.
Non-Liver Illnesses: Some tests, notably AST and ALP, may be elevated in muscle disease, bone disorders, or heart problems.
Age and Sex: Normal test ranges can differ by age and gender. Always compare results to laboratory reference values.

How Are Liver Function Tests Performed?

Liver function tests are conducted using a standard blood sample, usually drawn from a vein in the arm. Fasting may be recommended before some tests. Always notify your healthcare provider of medications or supplements you are taking before laboratory testing.

Frequently Asked Questions (FAQs)

Q: What symptoms might prompt a doctor to order liver tests?

A: Common symptoms include yellowing of the skin or eyes (jaundice), unexplained fatigue, abdominal pain, dark urine, pale stools, and swelling in the abdomen or legs.

Q: Can abnormal liver test results mean something other than liver disease?

A: Yes. Elevated enzymes like AST and ALP may come from muscle, heart, or bone issues and not necessarily from liver disease.

Q: Are liver tests useful for screening healthy people?

A: Liver tests are not typically performed on all healthy adults, but may be ordered if you have risk factors, take certain medications, or have a family history of liver disease.

Q: What should you do if your liver test results are abnormal?

A: An isolated abnormal result may not be cause for alarm. Your doctor will usually repeat tests, assess your symptoms, review your medical history, and possibly order further testing.

Q: Can liver tests predict how well a liver is working overall?

A: Liver tests provide valuable information but are only one part of a broader clinical assessment. Some severe liver disease can be present even with only modest changes in tests, and vice versa.

Key Takeaways

Liver function tests are indispensable in the screening, diagnosis, and monitoring of liver and some non-liver diseases.
Abnormal results should be interpreted in context with clinical findings and other tests.
Consult a healthcare provider to understand your specific circumstances and implications of any test result.

References

Author

Sneha TeteBeauty & Lifestyle Writer

Sneha is a relationships and lifestyle writer with a strong foundation in applied linguistics and certified training in relationship coaching. She brings over five years of writing experience to thebridalbox, crafting thoughtful, research-driven content that empowers readers to build healthier relationships, boost emotional well-being, and embrace holistic living.

Read full bio of Sneha Tete