Liver function tests (LFT) are blood tests that measure enzyme and protein levels in your blood. Abnormal results on LFT indicate that there's a problem affecting your liver, a situation that warrants further investigation. Liver function is tested to diagnose diseases such as hepatitis and cirrhosis, among others.
ALT
ALT stands for alanine aminotransferase. ALT is also known as serum glutamic pyruvate transaminase (SGPT). ALT is an enzyme, a protein that initiates a chemical reaction. An elevated ALT indicates inflammation or injury to the liver cells. ALT levels may be higher than normal in overweight people, who often have some degree of fat in their liver.
AST
AST stands for aspartate transaminase. AST is also known as serum glutamic-oxaloacetic transaminase, or SGOT. AST is an enzyme found in the liver and other parts of the body. An increase in levels of AST usually indicates liver damage or disease, though strenuous exercise may cause a temporary rise. Fatty liver also causes elevations in AST.
GGT
An elevated GGT, which stands for gamma-glutamyltransferase , along with elevated levels of alkaline phosphatase (ALP), indicates a problem with bile ducts, according to Palmer. Problems with blockage within the bile ducts is known as cholestatic liver disease. Normal levels of GGT are 3 to 60 IU/L. GGT is highly sensitive to alcohol use and some drugs that affect the liver, such as acetaminophen, and will rise transiently after a heavy dose.
ALP
The normal range of ALP, or alkaline phosphatase, is 35 to 115 IU/L. ALP is an enzyme found mostly in the liver and bile ducts, but also in bones, kidneys and intestines. According to liver disease expert Dr. Melissa Palmer, an elevated ALP level only indicates liver disease if the GGT is also raised.
Other Tests
Other liver function tests include measuring albumin and bilirubin. Measuring albumin, a protein synthesized in the liver, can indicate how well your liver is producing proteins, one of its most important functions, according to the Mayo Clinic.
Bilirubin is a byproduct of red blood cell breakdown, a function performed in the liver. An elevated bilirubin level will result in jaundice, the main symptom of which is yellowing of the skin and the whites of the eyes.
