Liver function tests
Also known as: liver panel, liver blood tests
A panel of enzymes and proteins that together show whether liver cells are injured, whether bile is flowing, and whether the liver is still doing its manufacturing job.
- Abbreviations
- LFTs, LFT
- Kind
- Test panel
- Categories
- Liver & hepatobiliary, Chemistry & metabolic
- Specimen
- Serum
- Method
- Chemistry analyser
- Terminology
- LOINC 24325-3
- Type
- Blood test
- Sample
- Blood from a vein
- Used for
- Jaundice, abdominal symptoms, alcohol, fatty liver, drug monitoring
- Measures
- Liver enzymes, bilirubin and albumin: injury, bile flow and synthesis
- Result
- A panel of numeric values, each with a laboratory reference interval; the pattern across the panel matters more than any single value
Why is it used?
- Jaundice, dark urine, pale stools
- Abdominal pain, nausea, itching
- Heavy alcohol use or viral hepatitis risk
- Monitoring statins, methotrexate, antiepileptics and many other drugs
- Fatty liver in obesity and diabetes
What does it measure?
| Component | What it measures | A higher value may be seen in | A lower value may be seen in |
|---|---|---|---|
| ALT (alanine aminotransferase) ALT ALT | Enzyme released from injured liver cells | Hepatitis, fatty liver, alcohol, drugs, congestion | Not clinically important |
| AST (aspartate aminotransferase) AST AST | Enzyme from liver, muscle, heart and red cells | Liver injury (alcohol-related if AST exceeds ALT), muscle injury, haemolysis | Not clinically important |
| ALP (alkaline phosphatase) ALP Alkaline phosphatase | Enzyme from bile ducts and bone | Cholestasis, bone disease, growth, pregnancy | Rare inherited deficiency, malnutrition |
| GGT (gamma-glutamyl transferase) GGT GGT | Enzyme induced by cholestasis, alcohol and drugs | Bile-duct obstruction, alcohol, fatty liver, enzyme-inducing drugs | Not clinically important |
| Bilirubin bili | Breakdown product of haemoglobin processed by the liver | Haemolysis, Gilbert syndrome, hepatitis, bile-duct obstruction | Not clinically important |
| Albumin alb | Main protein made by the liver | Dehydration | Cirrhosis, inflammation, malnutrition, kidney or gut protein loss |
| Prothrombin time / INR (often added) PT/INR | Clotting factor production by the liver | Severe liver injury, cirrhosis, vitamin K deficiency, warfarin | Not clinically important |
A high or low value can be associated with several different situations; the result is interpreted with other results, symptoms, history and clinical findings.
How is it performed?
Venous blood.
Specimen. Venous blood (serum)
Do I need to prepare?
None, though fasting improves consistency for some labs.
What do the results generally mean?
| Finding | What it may indicate |
|---|---|
| ALT and AST much higher than ALP | Hepatocellular injury: viral hepatitis, drugs, fatty liver, alcohol |
| ALP and GGT high with raised bilirubin | Cholestasis: gallstone in the bile duct, pancreatic tumour, some drugs |
| Low albumin and high INR | Loss of synthetic function: cirrhosis or acute liver failure |
| Isolated mildly raised bilirubin | Often Gilbert syndrome, a harmless inherited variation |
What can affect the result?
- Alcohol in the preceding days and weeks
- Obesity and fatty liver, which cause the commonest mild abnormalities
- Strenuous exercise and muscle injury (AST, and to a lesser extent ALT)
- Pregnancy (ALP), growth in childhood, fasting (bilirubin in Gilbert syndrome)
- Many medicines and herbal supplements
Medicines. Statins, paracetamol in overdose, antibiotics such as flucloxacillin and co-amoxiclav, antiepileptics, methotrexate, antifungals, antituberculous drugs and some herbal products can raise liver enzymes; oral contraceptives and anabolic steroids can cause cholestasis.
What can the test not tell you?
- How much scarring (fibrosis) the liver has: a normal panel does not exclude cirrhosis, and fibrosis is assessed with scores such as FIB-4, elastography or biopsy
- The cause of liver injury without further tests (viral serology, autoimmune antibodies, iron studies, ultrasound)
- True 'function' in most cases: the enzymes show injury, and only albumin and clotting reflect synthesis
Despite the name, they mostly detect damage rather than measure function; a normal panel does not exclude cirrhosis. Muscle injury raises AST, bone growth raises ALP.
Other tests commonly used with it
Medicines monitored with this test
Each medicine page cites the official document that names this test in its monitoring plan.
Catalogued concepts this page covers
Concepts of the master test taxonomy that resolve to this page; each links to its category.