The biomarkers below are tested as part of a Liver Function Test - Learn how to understand your Liver Function Test results and improve your numbers by registering for our free trial

Liver function are used to help diagnose and monitor liver disease or damage. The tests measure the levels of certain enzymes and proteins in your blood.

Some of these tests measure how well the liver is performing its normal functions of producing the proteins Albumin & Globulin, and the clearing of Bilirubin, a blood waste product. Other liver function tests measure enzymes that liver cells release in response to damage or disease [30].

None of the liver function tests are specific for a particular liver or biliary tract disease, thus the combination of the tests are much more powerful that the individual tests in isolation and results for each marker are generally viewed in context of the overall test [31].


Bilirubin is an orange-yellow waste product made during the normal breakdown of red blood cells. Bilirubin passes through the liver and is excreted out of the body. Bilirubin is also part of bile, which your liver makes to help digest the food you eat.  Direct (conjugated) bilirubin travels freely through your bloodstream to your liver. Most of this bilirubin passes into the small intestine. A very small amount passes into your kidneys and is excreted in your urine. Bilirubin that is bound to a certain protein is called indirect (unconjugated) bilirubin [32].


Albumin is one of several proteins made in the liver, and is one of two main proteins in your blood, the other being Globulin.   Since albumin can be low in many different diseases and disorders, it may be used in a variety of settings to help diagnose disease, to monitor changes in health status with treatment or with disease progression, and as a screen that may indicate the need for other kinds of testing [35].

An albumin test may be ordered as part of a liver panel to evaluate liver function OR as part of a renal panel to evaluate kidney function. Albumin may also be ordered to evaluate a person’s nutritional status [35].


Globulin is a generic term used to describe a set of sixty proteins including the antibodies or gamma globulins and protein-carbohydrate compounds known as glycoprotein. Globulins are one of two main proteins in the blood, the other being Albumin [35].

Total Protein

Total protein is the sum of the amount of Albumin and Globulin in the blood. Results of a total protein test are usually considered along with the other liver function test results as well as kidney and metabolic results.  Results give information on a person’s general health status with regard to nutrition and/or conditions involving major organs, such as the kidney and liver. However, if results are abnormal, further testing is usually required to help diagnose the disease affecting protein levels in the blood [37].

A/G Ratio

The albumin/globulin (A/G) ratio is the amount of albumin in the serum divided by the globulins. Because disease states affect the relative amounts of albumin and globulin, the A/G ratio may provide a clue as to the cause of the change in protein levels [37].

Alkaline phosphatase (ALP)

ALP is an enzyme in the liver, bile ducts and bone. Liver cells release increased amounts of ALP into the blood when there is liver damage [37].

Alanine transaminase (ALT)

ALT is an enzyme found mostly in the cells of the liver and kidney. When the liver is damaged, ALT is released into the blood. This makes ALT a useful test for early detection of liver damage.

ALT and Aspartate transaminase (AST) are considered to be two of the most important tests to detect liver injury, although ALT is more specific to the liver than AST. Sometimes ALT is compared directly to AST and an AST/ALT ratio is calculated. This ratio may be used to distinguish between different causes of liver damage and to help recognize heart or muscle injury.

ALT values are often compared to the results of other tests such as alkaline phosphatase (ALP), total protein, and bilirubin to help determine different causes of liver injury [40].

women. The prevalence of ALT elevation increased with increasing BMI [42].

Aspartate transaminase (AST)

AST is an enzyme found in cells throughout the body but mostly in the heart and liver and, to a lesser extent, in the kidneys and muscles. In healthy individuals, levels of AST in the blood are low. When liver or muscle cells are injured, they release AST into the blood. This makes AST a useful test for detecting or monitoring liver damage.

An AST test is often performed along with an ALT. Both are enzymes found in the liver that become elevated in the blood when the liver is damaged. A calculated AST/ALT ratio is useful for differentiating between different causes of liver injury and in recognizing when the increased levels may be coming from another source, such as heart or muscle injury [43].