LFT (Liver Function Test)
Understanding LFT (Liver Function Test)
What is LFT (Liver Function Test)?
An LFT (Liver Function Test) assesses the overall health of your liver. It helps diagnose and monitor liver disease or damage and monitor or track the recovery process of any known liver problems. It also helps determine if you need dose adjustments of medicines you might be taking. An LFT is also done as a part of routine preventive health checkups.
The liver is the largest organ situated in the right upper part of the belly. Interestingly, it is the only organ that can regenerate efficiently. It performs various vital bodily functions, including the metabolism of nutrients like fats, proteins, carbohydrates, and certain medicines. Also, the liver cleanses your blood (a process called detoxification) by converting toxins into waste products. Hence, keeping your liver healthy is essential to maintain your overall health.
An LFT (Liver Function Test) helps with the early detection of liver problems such as fatty liver disease, cirrhosis, jaundice, and hepatitis. Your doctor may advise an LFT if you experience symptoms such as chronic fatigue, belly pain, dark-colored urine, and yellowing of the skin or whites of eyes or have risk factors such as obesity, high blood pressure, diabetes, excessive alcohol consumption, or a family history of liver disease. Usually, no special preparation is required for an LFT (Liver Function Test). You may eat and drink normally as per your daily routine.
Test result ranges are approximate and may differ slightly between labs depending on the methodology and laboratory guidelines. Talk to your doctor about your specific test results. Narrate your complete medical history to help them correlate your clinical and laboratory findings. The test results will help the doctor determine your medical condition, make recommendations for lifestyle modifications such as diet and exercise, decide whether or not medication will be required to manage your liver health, and formulate your overall treatment plan.
What is LFT (Liver Function Test) used for?
An LFT (Liver Function Test) is done:
- As part of a routine health checkup.
- To diagnose or measure the progression of liver diseases, such as hepatitis, fatty liver disease, jaundice, liver cirrhosis, or liver cancer.
- To monitor the treatment response of existing liver disease.
- To monitor the effects of certain medications like penicillin, tetracycline, valproic acid, nonsteroidal anti-inflammatory drugs (NSAIDs), and high doses of paracetamol, as these may affect your liver function.
- To monitor for alcohol abuse.
What does LFT (Liver Function Test) measure?Contains 11 tests
An LFT (Liver Function Test) helps determine the health of your liver by measuring various components like enzymes, proteins, and bilirubin. These components help detect inflammation, infection, diseases, etc., of the liver and monitor the damage due to liver-related issues.
A Bilirubin Indirect test measures the amount of indirect or unconjugated bilirubin in your body. Bilirubin is a yellowish byproduct primarily produced when your body breaks down aged red blood cells (RBCs). When RBCs finish their lifespan of 120 days, they break down and pass to your liver. Indirect bilirubin, a form of bilirubin that is unconjugated (not soluble in water), is bound to the protein albumin that helps transport it to the liver. When the liver processes the bilirubin, it unbinds from the albumin and binds to a sugar molecule, making it water-soluble. This water-soluble bilirubin is mixed with bile, excreted in the bile ducts, and stored in your gallbladder. Finally, bile is released into the small intestine to help digest fat and is eventually excreted with your stool as a waste product.
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A Bilirubin Direct test measures the amount of direct or conjugated bilirubin present in your body. Bilirubin is a yellowish byproduct primarily produced when the body breaks down aged RBCs. When the RBCs finish their lifespan of 120 days, they break down and pass to the liver. In the liver, direct bilirubin–a form of bilirubin conjugated with glucuronic acid (sugar)–is processed, mixed with bile, and then excreted in the bile ducts and stored in your gallbladder. Finally, the bile is released into the small intestine where it is further broken down and helps digest fat. It is eventually excreted within your stool as a waste product.
Elevated levels of bilirubin can be indicative of various liver or bile duct issues. Additionally, higher bilirubin levels might result from an increased breakdown of red blood cells in the body.
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Gamma Glutamyl Transferase
Gamma-Glutamyl Transferase (GGT) is an enzyme found in various organs, with the highest concentration in the liver. Usually, this enzyme is present in low levels in the blood. However, when there is liver damage or disease, GGT is released into the bloodstream, causing an increase in GGT levels. In addition to the liver, GGT can also be elevated in conditions affecting the bile ducts or the pancreas. It is usually, the first liver enzyme to rise in the blood when there is any damage or obstruction in the bile duct, making it one of the most sensitive liver enzyme tests for detecting bile duct problems.
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A Bilirubin Total examination quantifies the levels of total bilirubin in the body, encompassing both indirect (unconjugated) and direct (conjugated) bilirubin. Bilirubin, a yellowish waste substance, is primarily generated during the breakdown of aging red blood cells (RBCs) in the body. After their typical lifespan of 120 days, RBCs disintegrate in the liver, leading to the production of a substantial amount of bilirubin. It is crucial for this bilirubin to be eliminated from the body.
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An SGPT test measures the amount of ALT or SGPT enzyme in your blood. ALT is most abundantly found in the liver, but it is also present in smaller amounts in other organs like the kidneys, heart, and muscles. Its primary function is to convert food into energy. It also speeds up chemical reactions in the body. These chemical reactions include the production of bile and substances that help your blood clot, break down food and toxins, and fight off an infection.
Elevated levels of ALT in the blood may indicate liver damage or injury. When the liver cells are damaged, they release ALT into the bloodstream, causing an increase in ALT levels. Therefore, the SGPT/ALT test is primarily used to assess the health of the liver and to detect liver-related problems such as hepatitis, fatty liver disease, cirrhosis, or other liver disorders.
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Alkaline Phosphatase (ALP)
An Alkaline Phosphatase (ALP) test measures the quantity of ALP enzyme present throughout the body. The main sources of this enzyme are the liver and bones. It exists in different forms depending on where it originates, such as liver ALP, bone ALP, and intestinal ALP. In the liver, it is found on the edges of the cells that join together to form bile ducts.
ALP levels can be increased during pregnancy as it is found in the placenta of pregnant women. It is also higher in children because their bones are in the growth phase. ALP is often high during growth spurts (a short period when an individual experiences quick physical growth in height and body weight).
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An SGOT test measures the levels of serum glutamic-oxaloacetic transaminase (SGOT), also known as aspartate aminotransferase (AST), an enzyme produced by the liver. SGOT is present in most body cells, most abundantly in the liver and heart. The primary function of this enzyme is to convert food into glycogen (a form of glucose), which is stored in the cells, primarily the liver. The body uses this glycogen to generate energy for various body functions.
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Protein Total, Serum
A Protein Total, Serum test measures the amount of proteins in the body. Proteins are known as the building blocks of all cells and tissues. They play a crucial role in the growth and development of most of your organs and in making enzymes and hormones. There are two types of proteins found in the body, namely albumin and globulin. About 60% of the total protein is made up of albumin, which is produced by the liver. It helps to carry small molecules such as hormones, minerals, and medicines throughout the body. It also serves as a source of amino acids for tissue metabolism. On the other hand, globulin is a group of proteins that are made by the liver and the immune system. They play an important role in liver functioning, blood clotting, and fighting off infections.
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This further contains
- Albumin/Globulin Ratio, Serum
- Globulin, Serum
- Serum Albumin
- Protein Total
Interpreting LFT (Liver Function Test) results
Alanine Aminotransferase (ALT)
The normal ALT levels range from 0-35 U/L.
Lower ALT levels indicate a healthy liver; however, lower levels can also be seen in patients with malnutrition.
A mild to moderate increase in ALT levels is seen in patients with alcoholic liver disease, cirrhosis, chronic liver disease, bile duct obstruction, liver trauma, or any physical injury, or patients taking certain medicines that are harmful to the liver.
A high increase in ALT levels is seen in patients with acute hepatitis like viral hepatitis (Hepatitis A, Hepatitis B, Hepatitis C) or in patients who have taken very high doses of some medicines like paracetamol.
Aspartate Aminotransferase (AST)
The normal AST test results range from 0-35 U/L.
Lower levels of AST in the blood are considered normal, although very low levels are seen in cases of alcoholic liver disease and malnutrition.
High levels of AST are seen in patients with alcoholic liver disease (AST often increases much more than ALT), cirrhosis, chronic liver disease, bile duct obstruction, liver trauma, non-alcoholic fatty liver disease (NAFLD), viral hepatitis (Hepatitis A, Hepatitis B, Hepatitis C) and in patients taking medicines that are harmful to the liver or taking very high doses of some medicines like paracetamol. High levels of AST are also seen in patients with heart attack and muscle injury (however, ALT levels are normal in these patients). A high level of AST with normal levels of ALT indicates that the source of AST is not the liver.
Alkaline phosphatase (ALP)
The normal level of ALP in the blood is 13-100 μ/L
High levels of ALP are seen in patients with bile duct obstruction, hepatitis, cirrhosis, and in liver cancer.
High levels of ALP are also seen in growing children and pregnant women and are considered normal.
Low levels of ALP are seen in patients with malnutrition and certain genetic disorders. ALP levels also decrease temporarily after heart surgery and blood transfusion.
Total Serum Protein
The normal level of Total protein in blood is 5.5-8.0 g/dL.
Albumin & Globulin
The normal level of Albumin is 3.5-5.5 g/dL, approximately 50-60%, and that of Globulin is 2.0-3.5 g/dL, approximately 40-50%. a normal A/G ratio of slightly over 1.
Albumin: Low levels indicate that you may suffer from a disorder where the protein isn't synthesized, digested, or absorbed properly. Lower levels are seen in patients with chronic liver diseases such as cirrhosis, inflammatory liver diseases like hepatitis, and hepatocellular necrosis. Higher levels are seen in liver infections like Hepatitis A, Hepatitis B, and Hepatitis C. High levels may also be seen if you are having a protein-rich diet or if you are dehydrated.
Globulin: Low levels are seen in patients with malnutrition. High levels are seen in chronic active hepatitis and alcoholic hepatitis. It is also increased in acute infection and chronic inflammatory diseases.
A/G Ratio: A low A/G ratio is indicative of overproduction of globulin and reduced production of albumin, which occurs with liver cirrhosis. A high A/G ratio often suggests the decreased production of globulins and is seen in some genetic diseases or leukemia.
The normal level of Total Bilirubin in the blood is 0.3-1.0mg/dL.
The normal level of conjugated bilirubin (direct) is 0.1-0.3mg/dL.
The normal level of unconjugated bilirubin (indirect) is 0.2-0.7mg/dL.
The lower levels are usually not a concern.
Unconjugated Bilirubin: Higher levels of unconjugated bilirubin are seen in patients with jaundice, acute hepatocellular damage, cirrhosis, viral hepatitis, alcoholic liver disease, bile duct obstruction, liver failure, and in conditions involving an unusual amount of RBC destruction (hemolysis). Increased levels are also commonly seen in newborns, typically 1 to 3 days old. If the bilirubin levels do not return to normal and are increasing rapidly, this may indicate neonatal jaundice.
Higher unconjugated bilirubin levels compared to conjugated bilirubin are suggestive of transfusion reactions and cirrhosis.
Conjugated bilirubin: Higher levels of conjugated bilirubin are seen in patients with hepatitis, gallstones, or inflammation of the bile duct (the duct that carries bile from the liver to the gut).
The normal level of GGT in the blood is 9-48 U/L.
High levels of GGT are seen in patients with obstructive liver disease, acute and chronic viral hepatitis, cirrhosis, fatty liver disease, cholestasis, alcoholic liver disease, and liver tumors, and in case the patient is taking medicines like phenobarbitone, phenytoin, paracetamol and antidepressants. The low levels of GGT in the blood indicate the absence of liver disease and confirm no alcohol consumption.
There are other conditions as well in which high GGT levels are seen as heart failure, pancreatitis, or diabetes. GGT levels are measured along with ALP. If both enzymes are elevated, it indicates liver disease. If GGT is normal and ALP is elevated, it indicates an underlying bone disease.
Note: Your doctor will interpret your results depending on your gender, age, medications/treatment, or diet you are taking.
Answers to Patient Concerns & Frequently Asked Questions (FAQs) about LFT (Liver Function Test)
Frequently Asked Questions about LFT (Liver Function Test)
Q. What is the full form of LFT?
Q. What is an LFT (Liver Function Test) used for?
Q. Is fasting required before an LFT (Liver Function Test)?
Q. What factors can affect my LFT (Liver Function Test) results?
Q. What do the elevated levels of LFT (Liver Function Test) mean?
Q. What are the early signs of an unhealthy liver?
Q. What can cause a fatty liver?
Q. How can I keep my liver healthy?
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- Lala V, Zubair M, Minter DA. Liver Function Tests. In: StatPearls [Internet]. Treasure Island, Florida: StatPearls Publishing; Jan. 2023 [Accessed 24 Jan. 2023]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482489/
- Liver Function Tests [Internet]. Stanford Medicine Health Care; [Accessed 24 Jan. 2023]. Available from: https://stanfordhealthcare.org/medical-tests/b/blood-test/types/liver-function-test.html
- Common Liver Tests [Internet]. Johns Hopkins Medicine; [Accessed 24 Jan. 2023]. Available from: https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/common-liver-tests