All You Need To Know About Liver Function Tests
Dr. Megha Zacharia

Dr. Megha Zacharia

May 17General wellness

All You Need To Know About Liver Function Tests

This article is compiled by Sanjana Varma, a freelance writer at Proactive For Her.

What is the function of the liver in my body?

Shaped like a cone, the liver is a dark reddish-brown organ that weighs about 3 pounds. The liver is located in the upper right-hand portion of the abdominal cavity, beneath the diaphragm, and on top of the stomach, right kidney, and intestines.

The liver’s major functions are in the metabolic processes of the body.

These include:

  • breaking down or conversion of glucose and poisonous ammonia
  • balancing energy metabolism by converting glycogen to glucose and storing extra glucose by converting it to glycogen
  • making toxins less harmful to the body and removing them from the bloodstream

What is the Liver Function Test (LFT)? Is your Liver-A-Okay?

Liver functions tests are done to evaluate how well your liver is functioning. It is used to screen for, detect, evaluate and monitor acute and chronic liver inflammation (hepatitis), infection, liver disease and/or damage, even damage due to medication. LFTs measure enzymes, proteins, and substances that are produced or excreted by the liver. This enables us to understand the decrease in its function or if there is any damage to the liver.

Who should take LFT?

Complete LFTs, or one or more components, may be ordered to understand if some have any liver dysfunction, disease or injury especially :

  • If you have a history of hepatitis or possible exposure to hepatitis viruses
  • If you consume alcohol and that has affected your liver tissue
  • If your family members had liver diseases
  • If you have taken any medication or recreational substances that might affect your liver

Usually, no one single set of liver tests are used to make a diagnosis. Often, several LFTs will be ordered to help determine the cause of the liver disorder. Abnormal tests on a liver function test panel may prompt a repeat analysis to see if the elevation or decrease persists and/or may indicate the need for additional testing to determine the cause of the liver dysfunction.

What are the symptoms of liver disease?

LFTs may be ordered when a person has signs and symptoms of liver disease or an infection such as hepatitis. Some of these include:

  • Weakness/fatigue
  • Appetite loss
  • Nausea
  • Vomiting
  • A bloated belly
  • Belly pain particularly in the upper right quadrant
  • Jaundice
  • Dark urine
  • Light coloured stool
  • Pruritus (itching)

LFT parameters and their importance

Let’s take a look at each of them separately:

1. Alanine Transaminase (ALT)

What is the test?

Alanine aminotransferase (ALT) is an enzyme found mostly in the cells of the liver. ALT is used by your body to metabolize protein and to convert it to energy.

What is the relevance?

  • In healthy individuals, ALT levels in the blood are low.
  • When the liver is damaged, ALT is released into the blood, usually, before more obvious signs of liver damage occur, such as jaundice. 
  • According to the American College of Gastroenterology, an ALT above 25 IU/L (international units per litre) in females and 33 IU/L in males typically requires further testing and evaluation.
  • A very high level of ALT is frequently seen with acute hepatitis. Moderate increases may be seen with chronic hepatitis.
  • People with blocked bile ducts, cirrhosis, and liver cancer may have ALT concentrations that are only moderately elevated or close to normal.

2. Aspartate Aminotransferase (AST)

What is the test?

Aspartate aminotransferase (AST) is an enzyme found in several parts of your body, including the heart, liver, and muscles. Since AST levels aren’t as specific for liver damage as ALT, it’s usually measured together with ALT to check for liver problems.

What is the relevance?

  • When the liver is damaged, AST can be released into the bloodstream. A high result on an AST test might indicate a problem with the liver or muscles. The normal range for AST is typically up to 40 IU/L in adults and may be higher in infants and young children.
  • When liver damage is due to alcohol, AST often increases much more than ALT (this is a pattern seen with few other liver diseases). AST is also increased after heart attacks and with a muscle injury.

3. Alkaline Phosphatase (ALP)

What is the test?

The ALP in blood samples of healthy adults comes mainly from the liver, with most of the rest coming from bones (skeleton). In the liver, ALP is found on the edges of cells that join to form bile ducts, tiny tubes that drain bile from the liver to the bowels, where it is needed to help digest fat in the diet.

What is the relevance?

  • ALP blood levels can be greatly increased, for example, in cases where one or more bile ducts are blocked. This can occur as a result of inflammation of the gallbladder (cholecystitis) or gallstones. 
  • Smaller increases of blood ALP are seen in liver cancer and cirrhosis, with the use of drugs toxic to the liver, and in hepatitis. Pregnancy can also raise ALP levels.
  • The normal range for ALP is typically up to 120 U/L in adults.

You may also need an ALP test if you’re taking a medication that has the potential to damage your liver, such as acetaminophen (Crocin).

4. Gamma-glutamyl transferase (GGT)

What is the test?

Is an enzyme found mainly in liver cells; it is a very sensitive marker for liver diseases, but it is not specific as it cannot differentiate between various causes of liver diseases. It is used in conjunction with ALP to determine the source of increased ALP, either from bone or liver. What is the relevance?

  • An elevation of gamma-glutamyltransferase (GGT) activity is seen in all forms of liver diseases, although the highest elevations are seen in the case of a blockage in the exit route of the liver. Elevated values can also indicate alcoholic liver damage or individuals who are heavy drinkers.
  • Increased GGT is also seen in medication mediated liver damage.  
  • If your results show an increase in GGT and alkaline phosphatase(ALP), it may be because of liver and gall bladder disease. Both ALP and GGT are elevated in the bile duct and liver disease, but only ALP will be elevated in bone disease.
  • A typical range for GGT levels in adults is between 5 and 36 international units per litre (IU/L).

5. Albumin, Globulin

What is the test?

The test measures the levels of two classes of proteins found in the blood, albumin and globulin.

  • Albumin is made by the liver and makes up about 60% of the total protein. Albumin keeps fluid from leaking out of blood vessels, nourishes tissues, and transports hormones, vitamins, drugs, and substances like calcium throughout the body.
  • Globulins make up the remaining 40% of proteins in the blood. The globulins are a varied group of proteins, some produced by the liver and some by the immune system. They help fight infection and transport nutrients.

The sum of the amount of albumin and globulin is reported as total protein.

The test also compares the amount of albumin with globulin and calculates what is called the A/G ratio. A change in this ratio can provide your doctor with an insight into the cause of the change.

What is the relevance?

Total protein levels may decrease in conditions that:

  • Interfere with the production of albumin or globulin proteins, such as malnutrition or severe liver disease
  • Increase the breakdown or loss of protein, such as kidney disease (nephrotic syndrome)
  • Increase or expand the volume of plasma, the liquid part of the blood (diluting the blood), such as congestive heart failure
  • Malabsorption is seen in inflammatory bowel disease

Total protein levels may increase with conditions that cause:

  • Chronic inflammation or infections such as viral hepatitis or HIV
  • Bone marrow disorders such as multiple myeloma
  • Dehydration

6. Bilirubin

Bilirubin is a waste product from the breakdown of red blood cells. It’s ordinarily processed by the liver. It passes through the liver before being excreted through your stool. This test measures the amount of bilirubin in the blood to evaluate a person's liver function or to help diagnose anaemias caused by RBC destruction.

What is the relevance?

  • Higher than normal levels of direct bilirubin in your blood may indicate your liver isn't clearing bilirubin properly. Elevated levels of indirect bilirubin may indicate an increased breakdown of Red blood cells or an inability of the liver to process bilirubin.
  • Bilirubin is of two kinds direct and indirect bilirubin. Normal results for a total bilirubin test are 1.2 milligrams per deciliter (mg/dL) for adults and usually 1 mg/dL for those under 18.

7. Prothrombin Time

What is the test?

A prothrombin time (PT) test measures the amount of time it takes for your blood plasma to clot. This is not a part of LFT but it is used to assess your liver function.

What is the relevance?

The liver produces the majority of coagulation proteins needed in the blood clotting cascade. Severe liver injury leads to reduction of liver synthesis of clotting factors and consequently prolonged PT. Prolonged PT (or INR) may also be due to other non-hepatic causes such as vitamin K deficiency, malabsorption and genetic clotting disorders.

A test in time saves life!

LFT results are not diagnostic of a specific condition. They indicate that there may be a problem with the liver. In a person who does not have symptoms or identifiable risk factors, abnormal liver test results may indicate a temporary liver injury or reflect something that is happening elsewhere in the body such as in the skeletal muscles, pancreas, or heart.

It may also indicate early liver disease and the need for further testing and/or periodic monitoring. Several sets of results from tests performed over a few days or weeks are often assessed together to determine if a pattern is present.

Many temporary conditions, such as shock, burns, severe infections, muscle trauma, dehydration, pancreatitis, haemolysis, and pregnancy can cause one or more of the liver function tests to be abnormal.

When liver disease is detected, it may be monitored regularly over time with the LFTs or with one or more of its components. Your doctor may decide to test you for hepatitis, other infections, or other diseases that can affect the liver. They may also choose to do imaging, like an ultrasound or CT scan. They may recommend a liver biopsy to evaluate the liver for fibrosis, fatty liver disease, or other liver conditions.

LFTs may also be ordered regularly to monitor the effectiveness of treatment for liver disorders. Go on, get tested. It’s not too late to take care of your health.


Disclaimer - This information is provided for educational purposes and should not be construed as medical advice. Please consult with your healthcare practitioners before undertaking any changes in your diet or adding supplements.

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