What are LFTs and KFTs?

The discourse of the biological apparatuses encompasses tests that have been an important medium to verify the problems that organs and blood constituents face in the human body. The tests that this article would cover are Liver Function Test and Kidney Function Test. Although, these tests are easily marketable and with the advancement of scientific medicine has discovered certain diseases that develop disastrous effects on human health for which these tests are very crucial. The liver is an important organ that deals with our digestive system and kidneys are one of the basic organs of the excretory system. Hence the functioning of these two organs is equally important like heart, lungs and brain! Now it is very beneficial for normal people to know how the tests are conducted and what the effects might be. Let us enter the lab of knowledge where we explain to you about these 2 tests:

Liver Function Tests (LFTs)

The health of your liver is measured by protein levels and enzymes that your liver encompasses or the bilirubin that is in your blood; all these can be conditioned by the Liver Function Test. LFT is done in the following scenarios:

  • In cases of infections of the liver like hepatitis C.
  • To know or assess effects of medications which involve the liver.
  • Any liver disease, such as cirrhosis, in which you need to find out the effectiveness of the treatment.

Liver Function Tests (LFTs) comprise of the following:

  • Alanine Transaminase (ALT).
  • Aspartate Aminotransferase (AST).
  • Alkaline Phosphatase (ALP).
  • Albumin and bilirubin tests.

Now let’s go more in depth about these liver function tests:

Alanine Transaminase Test in LFTs

Alanine transaminase (ALT) is an enzyme found in the kidney and liver, which helps in metabolization of the protein that is used by your body. When the liver fails to function, ALT gets released into the blood that increases its level. If this test yields a high result, then it may indicate that the liver is damaged. The normal range of ALT is 7-55 units per liter (U/L).

Aspartate Aminotransferase Test in LFTs

Aspartate Aminotransferase is an enzyme which is present in lot of regions of our body including the organs such as heart, liver and muscles.

However, AST levels do not very much specify liver damage and the ratio of ALT-AST is used to detect damage to the liver. In case of liver damage, AST gets released into the blood. Increased levels of AST are an indication of a problem in muscles or liver. The normal range of AST is 8-48 U/L.

Alkaline Phosphatase Test in LFTs

This enzyme is present in the bones, liver, and bile ducts. Higher levels of ALP indicate liver damage or blockage of bile. It may also indicate bone disease. ALP levels can hike among children and teenagers from bone growth. Pregnancy also increases the ALP levels. The normal range of ALP is 45-115 U/L.

Serum Albumin Test in LFTs

The prime protein of liver is Albumin. Albumin executes various bodily activities such as:

  • Stopping the fluid from leaking out of your blood vessels.
  • Tissue nourishment.
  • Hormone transportation, vitamins, and other substances throughout your body.
  • Albumin test checks the functioning of the liver in generating this protein. Lower the albumin, the poorer functioning of your liver. The normal range of albumin’s is 3.5–5.0 grams per deciliter (g/dL).

Bilirubin Test in LFTs

Red blood cells when broken down generate the waste product called Bilirubin. It is activated in the liver and is passed via it before one discards it by excretion. If there is liver damage, then it can’t properly process bilirubin and the level of bilirubin in blood will hike. Increased amount of Bilirubin indicates that the liver is not working efficiently. The normal range of bilirubin is 0.1-1.2 milligrams per decilitre.

Why Do I Need a Liver Function Test (LFT)?

Getting a liver test done helps in understanding the performance and efficiency of the function of the liver. Liver performs many important functions of the body such as:

  • Removing toxins from the blood.
  • Helping in conversion of nutrients from the diet we take.
  • Storing vitamins and minerals.
  • To regulate blood clotting.
  • Producing enzymes, bile and proteins.

How to Prepare for a Liver Function Test?

Doctors will provide with the complete instructions before undertaking the test. There may be certain medicines and food which can alter the levels of enzymes and proteins in the blood and should be avoided before undergoing LFT. Specific medications may be asked to stop. Eating restrictions might be instructed to the patient.

How is a Liver Function Test Performed?

In order to carry out LFT, your blood might be drawn out.

The skin will be cleaned by the person who conducts the test in order to prohibit any micro-organisms to harm your skin. A cuff or a tourniquet will be wrapped around your arm, which will increase the visibility of the veins. Then needles will be used to draw various samples of the blood out of your body. When the blood is withdrawn, the puncture site will be bandaged. The blood sample will be sent to the laboratory for testing.

What are the risks of Liver Function Tests?

Some of the common risks of Liver Function Tests are:

  • There may be bleeding under the skin.
  • Bleeding in excessive amount.
  • Infection.
  • Fainting.
  • Kidney Function Tests (KFT)

Signs which indicate kidney problems are:

  • High blood pressure.
  • Blood in urine.
  • The urge to urinate frequently.
  • The problem in urination at the beginning.
  • Pain during urination.
  • Swelling in the hands and feet.

Kidney Function Tests Consist Of The Following Tests:


Urinalysis helps in detecting traces of protein and blood in the urine. All the reasons for the protein in urine don’t signify diseases. Infection and heavy physical workout increase the protein in urine.

In urinalysis, 24-hour urine collection sample might be asked by the doctors. This would help the doctors to determine the level of creatinine in the body. The breakdown of muscle tissue produces creatinine.

Serum Creatinine Test in KFTs

This test checks the build-up of creatinine in the blood. The kidneys filter the creatinine from the blood. If the level of creatinine is high then it indicates a problem in the kidneys. If the creatinine is more than 1.2 milligrams/dl in women and 1.4mg/dl are in men then it indicates kidney problems.

Blood Urea Nitrogen (BUN) in KFTs

This particular test actually examines the waste product in the blood. BUN test determines the quantity of nitrogen in the blood. Protein when broken down produces urea nitrogen. BUN test is not always done to detect kidney damage. Usage of large doses of aspirin and some common medications will hike your BUN level. Certain drugs used are advised to be stopped before the BUN test is conducted. BUN level’s normal range is 7 and 20 mg/dl. Higher range than this indicates health problems.

Estimated GFR in KFTs

The functioning of your kidneys filtering is determined by this test, which is glomerular filtration rate or GFR test. Other than this test, the factors which are taken into consideration include: the test result, age, gender, race, weight and height. The ideal range for GFR test is 60 millilitres/minute/1.73m2. If it is lower than this range, then the kidneys are said to be at a risk for damage or disease.

Urine Sample in KFTs

Kidney tests require a 24-hour urine sample and blood samples. A 24-hour urine sample actually involves the creatinine clearance. This gives your doctor an estimate of your creatinine expelled from your system.

You need to urinate in the toilet normally on the day of your test. At the later part of the day and night use a special container to hold your urine. Cap the container and refrigerate it in the collection process. For the rest of the day and night, urinate into a special container provided by your doctor. Keep the container capped and refrigerated during the collection process. Label the container and alert your family members. Next morning urinate in the container. This completes the 24-hour collection process. The doctor’s instructions must be followed. Submit the sample to the proper resident.

Blood Samples in KFTs

Serum creatinine and BUN tests do need blood samples from the doctor’s office. Blood sample collector ties a tourniquet on your arm to make your veins more visible. They pierce the needle and draw out blood from the vein. The blood that is drawn out and collected in the test tube will be sent for analysis. The test would give you a slight pain in the part of your vein from where the blood is taken.

LFTs and KFTs: Conclusion

Both LFTs and KFTs help in determining the functioning of liver and kidneys and alert us to any problems with these organs. Most of the times, people concentrate on the heart and ignore other body organs. Not many realize the importance of other organs such as liver and kidneys to regulate our bodily activities.

Also Read:

Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:February 13, 2019

Recent Posts

Related Posts