What is a liver function test (LFT)?
Last content review 2026-09-23
The short answer
A liver function test (LFT) is a group of blood tests — usually ALT (SGPT), AST (SGOT), ALP, GGT, bilirubin, albumin and total protein — that show whether liver cells are irritated, whether bile flow is affected and how well the liver is making proteins. An LFT is a screening snapshot: it cannot diagnose fatty liver or measure scarring on its own.
What is happening?
Enzymes such as ALT and AST mainly reflect liver-cell injury; ALP and GGT are more linked to the bile ducts; bilirubin reflects how bilirubin is processed and cleared; albumin reflects the liver's protein-making capacity over time.
Reference ranges differ between laboratories, and values can be affected by recent exercise, medicines, alcohol and conditions outside the liver.
Why does this matter?
A normal LFT is reassuring but does not exclude fatty liver or fibrosis, which is why guidelines combine blood tests with risk factors, imaging and fibrosis scores such as FIB-4.
A persistently abnormal LFT deserves a planned evaluation rather than repeated testing without interpretation.
What does the evidence say?
MedlinePlus (US National Library of Medicine) describes LFTs as a panel measuring enzymes, proteins and bilirubin, and notes that abnormal results do not always mean liver disease.
The ACG clinical guideline on abnormal liver chemistries (2017) recommends interpreting the pattern of abnormalities (hepatocellular vs cholestatic) within the clinical context.
Key takeaway
An LFT tells your doctor where to look, not what the final answer is — read it as a pattern, alongside your risk factors.
Sources & references
US National Library of Medicine (MedlinePlus)
Liver Function Tests · Official health information
View original sourceAmerican College of Gastroenterology
ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries (2017) · Clinical guideline
View original sourceAmerican Association for the Study of Liver Diseases
AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease (2023) · Clinical guideline
View original source
This page is general health education. It is not a diagnosis, and it cannot replace advice from your treating doctor. Never start or stop a prescribed medicine based on what you read here.
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