Liver function test (LFT) blood test

What does the Liver Function measure?

An LFT measures enzymes (ALT, AST, ALP, GGT), bilirubin, and proteins (total protein, albumin, globulin) that together describe liver health.

Why is the Liver Function ordered?

It is ordered to look into fatty liver, the effect of alcohol or medication, jaundice, and to monitor known liver conditions.

Tests in this panel

Each test links to its own page with named reference-range sources.

Sources: [American Association for the Study of Liver Diseases (AASLD)] [CLSI] [AASLD]

• Total BilirubinThis measures the total amount of a yellow pigment that forms when old red blood cells are broken down. The liver takes up this pigment, chemically alters it, and sends it out in bile.
• Direct BilirubinThis is the water-soluble form (conjugated) that the liver has chemically changed by attaching a sugar group. Once altered, it can be excreted through the bile ducts into the gut.
• Indirect BilirubinThis is the unconjugated fraction, carried in the blood attached to albumin because it does not dissolve in water. The liver later attaches a sugar group so it can be excreted.
• ALT (SGPT)This enzyme sits inside liver cells and helps them process amino acids for energy. Damage to the cell membrane releases the enzyme into the bloodstream, raising the measured level.
• AST (SGOT)This enzyme helps cells convert amino acids for energy and is present in liver, heart, muscle, and kidney tissue. When any of those cells are damaged, the enzyme spills into the bloodstream.
• Alkaline Phosphatase (ALP)This enzyme sits on cell surfaces in the bile ducts, bone-building cells, and other tissues, where it removes phosphate groups. Its blood level rises when those tissues are more active or blocked.
• GGTThis enzyme lines the cells of the bile ducts and helps move certain molecules across cell membranes. Blockage or irritation of these ducts pushes more of the enzyme into the blood.
• Total ProteinThis adds up albumin and globulin, the two protein groups circulating in your blood. Albumin is made by the liver, while globulins include antibodies and transport proteins.
• AlbuminMade by the liver, this is the most abundant blood protein. It holds water inside blood vessels through osmotic pressure and ferries hormones, minerals, and medicines through the circulation.
• GlobulinGlobulin is a group of blood proteins that includes antibodies and carrier proteins. It is worked out by subtracting albumin from total protein.
• A/G RatioThe A/G ratio compares albumin with globulin. It shows the balance between the protein your liver makes and your immune proteins.
• AST/ALT RatioThis divides the AST level by the ALT level to give a proportion rather than a single number. Because each enzyme sits in different amounts across tissues, their proportion hints at the source of injury.
• AmmoniaThis nitrogen waste forms when gut bacteria and body tissues break down protein. The liver converts it into urea, a less toxic compound the kidneys can remove.

Frequently asked questions

What is included in the Liver Function?

An LFT measures enzymes (ALT, AST, ALP, GGT), bilirubin, and proteins (total protein, albumin, globulin) that together describe liver health. It typically reports 13 results: Total Bilirubin, Direct Bilirubin, Indirect Bilirubin, ALT (SGPT), AST (SGOT), Alkaline Phosphatase (ALP), GGT, Total Protein, and more.

Why is the Liver Function ordered?

It is ordered to look into fatty liver, the effect of alcohol or medication, jaundice, and to monitor known liver conditions.

How should the Liver Function be read as a whole?

No single value tells the full story — the results are read together, and each value is compared against the reference range printed on your own report, which can vary by lab, method and equipment.

Do the reference ranges in the Liver Function vary between labs?

Yes. Ranges depend on the laboratory's equipment and method, so the range printed on your own report is the one that applies to your result. Each test page names the standards body behind its range.