?A liver function test is a blood test used to check markers linked to liver health, bile flow, inflammation, injury and protein production. It is one of the most common blood tests requested in general health screening, medication monitoring, weight-loss checks, alcohol-related concerns and investigations for symptoms such as tiredness, nausea, abdominal discomfort or jaundice.
The name can be slightly misleading. A liver function test does not measure every function of the liver. It measures a group of enzymes, proteins and waste products that can give useful clues about how the liver and bile system may be coping.
At London Blood Tests, we offer private liver blood testing in London, with clinic and home visit appointments available. You can book a liver panel on its own or include it as part of a wider health assessment, metabolic panel, cholesterol test, HbA1c test, weight-loss monitoring profile or full blood test.
What is a liver function test?
A liver function test is a panel of blood markers used to assess the liver and related systems. The exact markers can vary between laboratories and panels, but common liver-related markers include ALT, AST, ALP, GGT, bilirubin, albumin and total protein.
These markers can help show whether there may be liver cell irritation, bile duct involvement, reduced protein production, inflammation, alcohol-related liver stress, medication effects or other patterns that need follow-up.
However, a liver blood test does not diagnose the exact cause by itself. It shows a pattern. That pattern then needs to be interpreted alongside symptoms, alcohol intake, medication history, weight, diabetes risk, cholesterol, viral hepatitis risk, family history and sometimes imaging such as an ultrasound.
A mildly raised result may be temporary. A persistently raised result may need further investigation.
What is liver function test in blood test?
People often search what is liver function test in blood test because the wording can feel vague. In practical terms, it means a laboratory checks specific substances in your blood that are linked to liver and bile duct health.
A standard panel may include:
· ALT
· AST
· ALP
· GGT
· bilirubin
· albumin
· total protein
· sometimes globulin
· sometimes LDH or clotting markers, depending on the panel
Each marker tells a slightly different part of the story. ALT and AST are enzymes often linked with liver cell irritation or injury. ALP and GGT can be linked with bile ducts and liver stress. Bilirubin can rise when the body has difficulty processing or clearing it. Albumin and total protein can provide information about protein production and general health.
The value is not only in one number. It is in the combination.
Liver function test blood work: what does it include?
The phrase liver function test blood work usually refers to the same group of liver markers taken from a venous blood sample. The blood draw itself is quick, but the interpretation can be more complex.
A liver profile may be used to check:
· liver enzyme levels
· bile duct markers
· bilirubin processing
· protein production
· possible medication effects
· alcohol-related liver stress
· metabolic liver risk
· possible inflammation or liver injury
· changes over time
It may be included in a full health screen because liver markers can be affected by lifestyle, medication, alcohol, infection, weight, diabetes risk, high triglycerides and fatty liver.
This is why a liver blood test is often paired with HbA1c, cholesterol, kidney function, full blood count, CRP, ferritin and sometimes hepatitis screening.
Liver function blood test: ALT explained
ALT stands for alanine aminotransferase. It is an enzyme found mainly in liver cells, although small amounts may be present elsewhere.
When liver cells are irritated or damaged, ALT can leak into the bloodstream. This can make ALT rise on a liver function blood test.
ALT may be raised with:
· fatty liver disease
· alcohol-related liver injury
· viral hepatitis
· medication effects
· supplement-related liver irritation
· obesity and insulin resistance
· recent illness
· intense exercise in some cases
· other liver conditions
A mild ALT rise is common and does not automatically mean serious liver disease. But if ALT is significantly raised, increasing over time, or raised together with other abnormal markers, it should be reviewed.
ALT is especially useful when interpreted with AST, GGT, bilirubin, ALP and metabolic markers.
AST explained
AST stands for aspartate aminotransferase. It is another enzyme checked in many liver function tests.
AST is found in the liver, but also in muscles, heart and other tissues. That means AST can rise for reasons that are not purely liver-related. For example, recent intense exercise, muscle injury or certain medical conditions can affect AST.
When both ALT and AST are raised, the pattern may help guide interpretation. A clinician may look at the degree of elevation, whether GGT is also raised, whether bilirubin is abnormal, and whether symptoms or risk factors are present.
AST should not be interpreted alone. It is one part of the liver panel.
GGT blood test: why it matters
A ggt blood test measures gamma-glutamyl transferase. GGT is an enzyme that is often used alongside other liver markers.
GGT can rise with liver and bile duct issues, but it is also commonly affected by alcohol intake, certain medications, fatty liver risk and metabolic health. A raised GGT does not automatically prove alcohol-related liver damage, but it can be a useful clue when reviewed with other markers.
GGT may be considered alongside:
· ALT
· AST
· ALP
· bilirubin
· cholesterol
· triglycerides
· HbA1c
· fasting glucose
· body weight and waist circumference
· alcohol intake
· medication and supplement history
If ALP is raised, GGT can also help clarify whether the pattern may be liver or bile duct related, rather than coming from another source such as bone.
ALP and bilirubin explained
ALP stands for alkaline phosphatase. It can be linked with bile duct activity, but it is also found in other tissues, including bone. This is one reason an isolated ALP rise needs careful interpretation.
Bilirubin is a yellow waste product made when the body breaks down old red blood cells. The liver normally processes bilirubin so it can be removed from the body. If bilirubin rises, it may cause yellowing of the skin or eyes, known as jaundice, although mild bilirubin changes may not always be visible.
Raised bilirubin may be linked with liver disease, bile duct obstruction, red blood cell breakdown, inherited conditions such as Gilbert’s syndrome, or other causes. The pattern matters.
For example, raised bilirubin with raised ALP and GGT may suggest a different issue from raised bilirubin with otherwise normal liver enzymes.
Albumin and total protein
Albumin is a protein made by the liver. Total protein measures albumin and other proteins in the blood.
Albumin can be affected by liver disease, kidney disease, inflammation, nutrition and other health conditions. Low albumin does not automatically mean the liver is failing, but it is an important marker when reviewed with the rest of the panel.
In routine private blood testing, albumin and total protein help complete the picture. They are especially useful when someone has swelling, long-term illness, unexplained weight changes, chronic inflammation or suspected liver, kidney or nutritional concerns.
Liver function test results: how to read them
Liver function test results should be read as a pattern, not as isolated numbers.
One slightly raised marker may mean very little by itself. Several abnormal markers together may suggest a clearer direction. A result that is getting worse over time is more important than a one-off borderline result. Symptoms, medication, alcohol, weight, diabetes risk and recent illness all change the meaning.
When looking at results, a clinician may consider:
· which markers are abnormal
· how high or low they are
· whether the pattern suggests liver cell injury or bile duct involvement
· whether bilirubin is raised
· whether albumin is low
· whether GGT is raised
· whether the result is new or persistent
· whether there are symptoms
· whether medicines, supplements or alcohol could be involved
· whether further testing or imaging is needed
This is why result interpretation should be done carefully. A liver panel can be useful, but it is not a full diagnosis on its own.
Abnormal liver function test: what can cause it?
An abnormal liver function test can happen for many reasons. Some are temporary and mild. Others need medical follow-up.
Possible causes include:
· recent viral illness
· fatty liver disease
· alcohol intake
· certain medicines
· herbal supplements
· anabolic steroids
· viral hepatitis
· gallstones or bile duct problems
· obesity
· insulin resistance