Your liver is one of the hardest-working organs in your body, performing over 500 vital functions every day. From filtering toxins and metabolising medications to producing proteins and storing energy, the liver is essential for life. Liver function tests (LFTs) are a group of blood tests that help assess how well your liver is working and can detect early signs of liver damage or disease.
Understanding your LFT results empowers you to take proactive steps toward protecting your liver health. This guide breaks down each component of a liver function test panel and explains what your results may mean.
What Are Liver Function Tests?
Liver function tests, also called a hepatic panel or liver panel, measure various enzymes, proteins, and substances in your blood that are produced by or processed by the liver. Despite the name, LFTs do not directly measure liver "function" – rather, they detect markers that indicate liver cell damage, inflammation, or problems with bile flow.
A standard LFT panel typically includes:
Let us examine each of these markers in detail.
ALT (Alanine Aminotransferase)
ALT is an enzyme found primarily in liver cells. When liver cells are damaged or inflamed, ALT leaks into the bloodstream, causing elevated levels. ALT is considered the most specific marker for liver damage because it is found mainly in the liver.
Normal range: 7-56 U/L (varies by laboratory)
Optimal for longevity: Below 25 U/L for men, below 20 U/L for women
Elevated ALT may indicate:
AST (Aspartate Aminotransferase)
AST is another enzyme released when liver cells are damaged. However, AST is also found in the heart, muscles, kidneys, and brain, making it less specific to the liver than ALT. The ratio of AST to ALT can provide additional diagnostic information.
Normal range: 10-40 U/L (varies by laboratory)
AST:ALT ratio significance:
Elevated AST may indicate:
ALP (Alkaline Phosphatase)
ALP is an enzyme found in the liver, bones, kidneys, and intestines. In the context of liver health, elevated ALP typically indicates problems with bile flow (cholestasis) rather than direct liver cell damage.
Normal range: 44-147 U/L (varies by age and sex)
Elevated ALP may indicate:
When ALP is elevated, GGT testing helps determine whether the source is liver or bone – if GGT is also elevated, the liver is likely the source.
GGT (Gamma-Glutamyl Transferase)
GGT is an enzyme found in the liver and bile ducts. It is particularly sensitive to alcohol consumption and is often elevated even with moderate drinking. GGT is also a useful marker of oxidative stress.
Normal range: 9-48 U/L for men, 9-36 U/L for women
Optimal for health: Below 25 U/L
Elevated GGT may indicate:
Bilirubin
Bilirubin is a yellow pigment produced when red blood cells break down. The liver processes bilirubin and excretes it into bile. Elevated bilirubin causes jaundice – yellowing of the skin and eyes. For more detailed information, read our guide on bilirubin testing.
Normal ranges:
Elevated bilirubin may indicate:
Albumin
Albumin is the most abundant protein in blood, produced exclusively by the liver. It helps maintain fluid balance in your body and transports various substances. Albumin levels reflect the liver's synthetic (production) capacity.
Normal range: 35-50 g/L
Low albumin may indicate:
Albumin takes weeks to change, so low levels typically indicate chronic rather than acute liver problems.
Total Protein
Total protein measures all proteins in your blood, including albumin and globulins (antibodies and other proteins). It provides additional context for interpreting other LFT results.
Normal range: 60-83 g/L
Abnormal total protein may indicate:
Patterns of Liver Test Abnormalities
Healthcare providers often look at patterns across multiple LFT markers to help identify the underlying cause:
Hepatocellular pattern (liver cell damage):
Cholestatic pattern (bile flow problems):
Mixed pattern:
Common Causes of Abnormal LFTs
Many factors can cause abnormal liver function tests:
When to Be Concerned
Mildly elevated liver enzymes are common and often resolve on their own. However, seek medical advice if:
Supporting Your Liver Health
To maintain healthy liver function:
Book Your Liver Function Test
Regular monitoring of your liver health is an important part of preventive healthcare. At Private Blood Tests London, we offer comprehensive liver function testing at our CQC-registered clinic in South Kensington. Our experienced team ensures accurate results delivered quickly and securely.
Learn more about [liver health and what blood tests reveal](/blog/liver-health-matters-what-blood-tests-can-reveal-about-this-vital-organ), and explore our [liver function test services](/liver-function-test).
Take charge of your liver health – book your liver function test today.