Dr. Ertan Beyatlı

What is LFT? When is it done?

(Update: ) - Digestive System Diseases

It is a group of biochemistry tests that are used to understand the health status of the liver.

(Liver Function Tests = Liver Function Tests). It is abbreviated as KCFT or KFT in Turkish. It is written as LFT in English.

  • LFT (or KFT) = Liver Function Tests
  • LFT = Liver Function Tests

It is the testing of metabolites made in the liver in the blood. Any abnormality in these tests indicates a problem with the liver.

What does the liver do?

Liver upper right of the abdomen It is the second largest organ of our body (our largest organ is the skin) located on the side just below the rib cage. It converts the sugar taken from foods into glycogen and stores it and takes part in the digestion of protein and fats taken from foods.

It produces albumin, the main protein of the body, and produces coagulation factors. It is involved in detoxifying and disposing of toxic substances and drugs that are formed in our body or taken from outside. It produces bile acids and bilirubin, which are released from the breakdown of blood and waste materials. Bile is a yellow black substance, made in the liver gall bladderIt is stored in the stomach, poured into the intestine with food and used in digestion of fats.

Normal values ​​of liver function tests may differ between laboratories. So comparing results from different laboratories can be difficult, as normal values ​​also vary depending on male / female gender and age.

Where are liver function tests used?

Liver function tests are used in the diagnosis of liver diseases. The height of the tests depends on the cause of the damage in the liver. Liver function tests are also used to monitor liver diseases. The response of the disease to treatment, recovery of the damage, and liver function tests are followed. These tests are frequently checked when using medications to touch the liver. These tests are checked frequently in the follow-up of diseases that can cause chronic liver damage such as hepatitis.

What are liver function tests?

The liver carries out many metabolic functions at the same time, and many metabolic substances are mixed with bile and blood. One or more of these substances are increased depending on liver diseases. These tests, which are used to reveal the health status of the liver, are called liver function tests. From liver function tests:

  • AST and ALT liver damage,
  • GGT and ALP damage in the bile ducts along with the liver,
  • Albumin, coagulation tests and INR indicate liver dysfunction.
AST and ALT elevation
AST and ALT elevation

Normal values

Normal values ​​(upper and lower limits) of Liver Function tests are as follows:

  • ALT = 7-55 U / L
  • AST = 8-48 U / L
  • ALP = 45-115 U / L
  • Albumin = 3.5-5.0 g / dL
  • Total protein = 6.3-7.9 g / dL
  • Bilirubin = 0.1-1.2 mg / dL
  • GGT = 9-48 U / L
  • LD = 122-222 U / L
  • PT = 9.5-13.8 seconds

* (U / L = units per liter, g / dL = grams per deciliter, mg / dL = milligrams per deciliter) Source: MayoClinic

Alanine Transaminase (ALT):

Also called Serum Glutamic Pyruvic Transaminase (SGPT). It is an enzyme and is used during protein production. It enters the bloodstream with the breakdown of liver cells. It is the most commonly used test to detect liver damage. In liver damage, too much is mixed with the blood and ALT rises.

ALT is found only in the liver. In other words, high ALT means there is damage to the liver. The ALT test is ordered to follow the diagnosis of liver diseases or the treatment of those with the disease and to understand whether the treatment is working or not. For this purpose, it may only be ordered in conjunction with ALT or other tests. ALT is more valuable than AST in the diagnosis and monitoring of liver diseases.

Aspartate Aminotransferase (AST):

Also called Serum Glutamic Oxaloacetic Transaminase (SGOT): it is an enzyme located inside liver cells and used in protein production. With the breakdown of liver cells, it enters the blood and its amount increases. AST is found not only in the liver but also in the heart and skeletal muscles. AST elevation indicates a liver, muscle or heart problem.

ALT / AST ratio also gives an idea about liver disease. During chronic hepatitis, while ALT> AST, after cirrhosis begins, AST> ALT. AST / ALT> 2 is seen in alcoholic and toxic liver diseases, and <1 in alcoholic and non-toxic liver diseases.

Alkaline Phosphatase (ALP):

The alkaline phosphatase enzyme is found in liver cells and bones near the bile ducts. It increases in liver and bone diseases. It increases with GGT in bile duct obstructions. GGT is normal, only ALP elevation is seen in bone diseases or diseases and tumors involving the bone marrow. Since bone formation rate is high in young people, ALP is high in young people. Since ALP is made in the placenta in the last three months of pregnancy (third trimester), it is found to be high.

Gamma Glutamic Transferase (GGT):

It is found in liver cells close to the bile ducts. It is the enzyme that concerns the bile ducts and increases with ALP in the obstruction of the bile ducts. If GGT high ALP is normal, it is due to causes such as alcohol, drugs, poisoning. Alcohol is metabolized and excreted in the liver and GGT is used during this process. GGT increases with excessive alcohol intake.


It is the body's main protein produced in the liver. It is abundant in the blood. In some liver diseases, albumin production is impaired and its amount in the blood decreases.

Total protein:

It is the measurement of albumin and other proteins in the blood. Along with albumin, coagulation factors and other proteins are also produced in the liver. In some liver diseases, protein production is impaired and its amount in the blood decreases.


It is the substance that gives the color of the green black colored bile. Increased bilirubin in the blood causes jaundice. Bilirubin is made from hemoglobin, the blood molecule. The hemoglobin released when the blood cells that fill their life are broken down is converted to bilirubin and brought to the liver where a sugar is added to the bile and this is called conjugated bilirubin. At the height of bilirubin, it is first checked which part is high and the average ratio of conjugated / unconjugated bilirubin is equal.

Conjugated bilirubin increased means there is a problem with the excretion of bile. Gallstone etc. Conjugated bilirubin increases due to obstructed bile ducts with obstructed bile ducts or in cases that obstruct the internal bile ducts such as hepatitis, due to alcohol intake for a long time or because the bile ducts are also blocked in pancreatic head tumors.

Unconjugated Bilirubin (Unconjugated Bilirubin) increase: It occurs as a result of excessive destruction of blood cells. Hemolytic anemia, hematoma etc. seen in diseases.

Lactate Dehydrogenase (LDH)

It is commonly found in many tissues. There is a large amount of LDH in the Liver, Muscle, Kidneys, Lung, Heart and blood. It increases in many diseases, including liver diseases, even during pregnancy and heavy exercise.

Coagulation tests and INR

Most of the clotting factors are produced in the liver. In some liver diseases, the production of these substances is interrupted and coagulation problems occur. It is an important test required to evaluate the synthesis function of the liver. For this reason, coagulation tests are one of the important tests that show the functioning of the liver.

Other tests

These are the tests required for further investigation and diagnosis of disorders in liver function tests.

Immunological tests

Viral hepatitis serology

It is requested to detect viruses that cause disease in the liver. There are 5 known hepatitis viruses. The tests used to detect hepatitis A, B, C, D and E. Hepatitis viruses are also called viral markers.


They are antibodies that attack liver tissue and cause diseases called autoimmune diseases. The most common autoimmune diseases: - Primary biliary cirrhosis: (antimitochondrial antibody - AMA), - Autoimmune hepatitis (Smooth muscle antibody - Anti Sm), - Primary sclerosing cholangitis (antinucleer cytoplasmic antibody - ANCA).

Tests required for the detection of liver metabolic diseases:

These are the tests used in the diagnosis of liver diseases caused by enzyme deficiency. - Wilson's disease is destroyed due to copper accumulation in the liver and ceruloplasmin is checked in the blood. - Cystic fibrosis is a rare cause of cirrhosis, alpha 1 antitrypsin is checked in the blood.

Liver biopsy: It is a very important test used to determine the degree of liver damage. Display methods liver ultrasound is the most preferred one. It is a fast, easy and effortless application, and it is the most used method in the detection of lesions that take up space in the liver. In addition, liver tomography and Magnetic Resonance imaging are frequently used tests in the diagnosis of liver damage.

Approach to abnormal liver function tests

Drugs and intoxications should be the first thing to come to mind in abnormalities in liver function tests.

While other liver function tests are normal, only bilirubin elevation:

The first thing to look at at the height of bilirubin is which section is elevated. Conjugated and Unconjugated bilirubin ratios are equal on average.

  • Unconjugated hyperbilirubinemia: In other words, the blood cells were broken down and bilirubin was made, but sugar could not be added to the liver.
    • Hemolysis: that is, excessive blood breakdown. It may be due to many diseases. It may occur due to abnormalities in blood cells.
    • Medicines,
    • Gilbert syndrome,
    • Crigler Najjar syndrome
  • Conjugated hyperbilirubinemia: In other words, blood cells are broken down and bilirubin goes to the liver and sugar is added but cannot be discarded.
    • Dubin-johnson syndrome,
    • Rotor syndrome,
    • Chronic liver diseases (in this case, some other liver tests are also abnormal).

Cholestatic picture

ALP and GGT elevation is more pronounced than AST and ALT

Liver function disorders due to bile duct obstructions: ALP and GGT elevation is higher than AST-ALT elevation in bile duct obstructions. Bile duct obstruction may be due to thin bile ducts (intrahepatic) in the liver or main bile ducts and gallbladder (extrahepatic) obstruction coming out of the liver. Conjugated bilirubin is usually high in bile obstruction.

  • Causes of intrahepatic bile duct obstruction:
    • Acute viral hepatitis
    • Primary biliary cirrhosis
    • Depends on medication,
    • Toxic (due to poisoning),
  • Causes of extrahepatic bile duct obstruction:
    • Stone in the common bile duct
    • Pancreatic head tumor,
    • Medicines
      • Erythromycin,
      • Antidepressant medications,
      • Birth control drugs,
      • Testosterone and anabolic steroids,
    • Heart failure,
    • Primary biliary cirrhosis; it is more common in women and the first finding is an increase in ALP,
    • Primary sclerosing cholangitis,
    • Liver cancers and liver metastases,
    • Familial.

Hepatitis table

If AST and ALT elevation is more prominent than ALP and GGT, it is called hepatitis table.

The table in which AST and ALT, among the liver function tests, increase more than ALP and GGT, is called the hepatitis picture. It indicates serious damage and inflammation in the liver. It usually occurs with hepatitis viruses.

  • Acute viral hepatitis
    • May be due to Hepatitis A, Hepatitis B, Hepatitis C and Hepatitis E.
  • Chronic viral hepatitis
    • Hepatitis B, Hepatitis C, and Hepatitis D infection,
  • Other viral hepatitis
    • CMV hepatitis,
    • EBV hepatitis,
  • Alcohol
    • Acute alcoholic hepatitis: causes severe and severe liver damage, occurs due to excessive alcohol intake at one time, and GGT is also increased.
    • Alcoholic fatty degeneration is liver damage due to long-term alcohol intake.
  • Cirrhosis (the biggest cause of cirrhosis is alcohol),
  • Drugs: Transaminases AST and ALT> 1000 / IU / L.
    • Phenytoin, carbamazapine, isoniazid, statins, methotrexate, paracetamol poisoning, amiodarone.
  • Liver tumors or liver metastases,
  • Hemochromatosis
  • Metabolic liver diseases (glycogen storage diseases and Wilson's disease),
  • Ischemic liver damage
  • Fatty liver (Transaminases AST and ALT are <100IU / L)
  • Causes of hepatitis picture due to reasons other than liver diseases:
    • Thyroid diseases,
    • Celiac disease,
    • Hemolytic anemias.

Isolated ALP height:

While other liver enzymes are normal, only ALP is elevated,

  • Pregnancy (ALP increases in the blood as Alkaline Phosphatase is made in the placenta in the third trimester of pregnancy, ie the last 3 months. Other Liver tests are normal).
  • Extra-Liver Bone or Kidney-related ALP elevation: (In osteoporosis, ALP does not increase without fracture).
    • Bone fracture
    • Paget's disease of the bone,
    • Osteomalacia,
    • Bone metastases of tumors.

Isolated GGT height:

While other liver enzymes are normal, only Gamma Glutamic Transferase GGT elevation:

  • Alcohol intake
    • It is the most common cause of GGT elevation,
    • Does not depend on the amount of alcohol,
    • It can be found normal in many alcoholics,
    • It is expected to return to normal in 4 weeks after quitting alcohol,
  • Medicines.

Rarely, hepatitis picture and cholestasis picture are confused with each other, and every 4 parameters increase equally. (source: Dr. Aydoğan LERMİ)

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