Types of Liver Function Tests and Their Normal Ranges

Most liver dysfunctions are asymptomatic in the beginning. Liver Function Test is a blood investigation to assess the functioning of liver and biliary system.

Liver is the largest gland of the body that is responsible for the secretion of the digestive juices that aid in metabolism of food. It is located in the upper right portion of the abdomen. Besides stimulating digestions, liver also performs several vital functions in the body without which, it would be impossible to survive. For example, liver is responsible for storing fats, minerals, fat-soluble vitamins and glucose in the form of glycogen. It also helps in the processing and distribution of proteins and secretion of vital clotting factors. Most importantly, liver is the primary organ that helps in the metabolism of drugs and exogenous hormones. These functions are helpful in the detoxification of the body from toxins and poisons.

Liver function test is one of the most common analytical methods used to identify the function of your liver; healthcare providers do this by evaluating the serum level of different enzymes and associated protein levels. Liver function test is helpful in diagnosing any abnormalities or disorders of the liver or the body in general.

Types of Liver Function Tests


Sometimes known as SGPT, when the levels of ALT are raised this could be an indication of liver inflammation of infection. Mainly, ALT functions in processing proteins and distributing them throughout the body.


Also be known as SGOT, ALT is found in many other body tissues besides liver and it plays a main role in protein manufacturing. When liver damage occurs due to inflammation or infections, serum ALT levels increase because they leak from ruptured and damaged cells.


Alkaline phosphate is an important enzyme, which is most frequently used for the assessment of biliary function. High levels are suggestive of biliary duct obstruction and may impending temporary or permanent liver damage. It is found in different body tissues and is generally high in younger ones. Raised levels indicate pathology in liver and biliary system.


Bilirubin is the by-product of red blood cell metabolism, which is excreted out of the body via liver in the form of bile. If any pathology affects the production or excretion of bilirubin from the body, it may result in accumulation within the tissues that may lead to illness. Since bilirubin is yellow in color, systemic accumulation leads to yellowish discoloration of sclera and skin (also referred to as jaundice in medical terms).

There are two forms of bilirubin in the body: total bilirubin and direct bilirubin. Total bilirubin indicates total levels of bilirubin in blood, and direct bilirubin levels indicate the amount of bile metabolized by the liver. Detection of relative concentration of total and direct bilirubin helps in the diagnosis of primary issue and site of disorder.

Albumin and Total Protein

Albumin is the main protein produced and distributed by the liver in the blood. It can be used as an indication of how efficiently your liver is functioning; abnormally high or abnormally low levels of albumin indicate pathology of the liver and the biliary system.

What Results Are Normal?

Here is a list of some important parameters with their normal ranges for liver function tests. These ranges can differ as per age, sex and pathological state of a body. Results can also differ with the use of certain drug and foodstuff.

[U= unit, dl= deciliter, L= liters, mg=milligrams, g=grams]

  • ALT: 7 to 55 units per liter (U/L)
  • AST: 8 to 48 U/L
  • Alkaline phosphate:45 to 115 U/L
  • Albumin:3.5 to 5.0 grams per deciliter (g/dL)
  • Total protein: 6.3 to 7.9 g/dL
  • Bilirubin:0.1 to 1.0 mg/dL

What to Do Before a Liver Function Test

Although a liver function test does not need any special preparations (unlike a sugar test), certain things can be done to helpget accurate results.

Avoid drinking water for at least eight hours before the test. If you have recently taken any medicines, inform your doctor about it. Also avoid foods and beverages that may affect your results. Sometimes drugs and some nutritional constituents can also interfere with the enzyme levels. In addition, if you are in a hurry, or want the process to be rushed, wear short sleeves of shoulders above your arm to aid blood extraction.

What to Except in Liver Function Tests

  • During the test: LFT is essentially a blood test, which is taken from the vein of your arm. An arm is ideally bent at 70 to 90 degrees to allow efficient blood extraction. As the needle pricks in your arm, it might sting lightly, which can be followed by some discomfort afterward that does not last for longer than a few hours. The blood is transferred from a small pipe into a tube containing an anti-coagulant to maintain the contents of blood until analysis is performed.
  • After the test: Either this sample is sent to a laboratory in the clinical vicinity or outside the main campus; results can then be supplied within hours.

Why Do You Need to Take Liver Function Tests?

Some people may have a doubt that why should they take liver function tests. Here are some reasons that you need to take live function tests:

  • An LFT can be used as a conclusive evidence to determine the cause of anomalous symptoms such as pale skin, dark urine or pain in the right part of abdomen.
  • Most frequently it is used as a part of your annual health checkup regimen, as suggested by your doctor.
  • This test can be used to diagnose cancer, carcinomas and other underlying pathologies in the body.
  • LFT's are used to check the progress of an ongoing treatment or therapy.
  • To identify secondary cancers in addition to other diagnostic tests such as X-rays, CT scans, etc.

Here is a video regarding all details about a liver function test:



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