Test Detail
Interpreting Results
Tests Included

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Written by
Dr. Shreya Gupta
BDS, MDS - Oral and Maxillofacial Pathology
Reviewed by
Dr. Lalit Mohan Gupta
MBBS, MD - Microbiology
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Kidney Function Test

KFT Test Includes 4 testsView All
Kidney Function Test
You need to provide
This test is for
Male, Female
Test Preparation
  1. Do not eat or drink anything other than water for 8-12 hours before the test.


What is KFT?

Kidneys play an important role in the removal of waste products and maintenance of water and electrolyte balance in the body. Kidney Function Test (KFT) includes a group of blood tests to determine how well the kidneys are working.

Why is KFT done?

The Kidney Function Test is performed:

·         As a part of routine health checkups

·         To help diagnose any disease affecting the kidneys

·         To screen people at risk for the development of any kidney diseases

·         To monitor treatment efficacy of kidney diseases

What does KFT Measure?

The kidneys are a pair of bean-shaped organs located on either side of the spinal column in the abdomen towards the back. The kidneys perform a number of important functions. The most important of these is that they filter the blood and separate the waste products generated out of regular metabolic activities of the body, primarily urea. Following the separation, the kidneys excrete the waste products out of the body through urine. They help in maintaining the normal pH level and water balance of the body. The kidneys also play essential roles in the synthesis of Vitamin D and Red Blood Cells (RBCs).

The Kidney Function Test includes the following tests to monitor kidney function:

·        Blood Urea Nitrogen (BUN)/ Urea:

Blood Urea Nitrogen is a test to measure the amount of urea nitrogen present in the blood. Urea is a nitrogenous by-product of the metabolism of protein, and its level in blood serves as an indication of the amount of nitrogen present in blood as urea. In simpler terms, BUN is the measure of the amount of nitrogen present in blood in the form of urea. High BUN levels in the blood can be caused as a result of kidney diseases, dehydration and obstruction in the urinary tract due to kidney stones, prostate gland enlargement, etc.

Urea test measures the level of urea in the blood. Urea is a final waste product formed from the breakdown of proteins. Urea is filtered out of the blood by the kidneys to excrete excess nitrogen present in the blood through urine. Excess of urea in blood is called uremia and can be caused by a number of conditions including kidney diseases.

·         Uric Acid:

This test measures the level of uric acid in the blood. Uric acid is a waste product formed from the breakdown of purines, which are essential building blocks of DNA. It is also produced by the metabolism of proteinaceous food, especially red meat. Uric acid is excreted from the body by the kidneys through urine and a small portion through stool. The uric acid test indicates the level of uric acid in the blood and serves as an indirect estimation of the proper functioning of the kidneys.

The presence of excess amounts of uric acid in the blood is called hyperuricemia, and causes gout due to the accumulation of uric acid crystals in the synovial fluid between joints. Hyperuricemia also causes the formation of hard lumps of uric acid crystals called tophi under the skin and at the top of the ears. Uric acid crystals can also accumulate in the kidneys and cause kidney stones.

·         Creatinine:

This test measures the level of Creatinine in blood. Creatinine is a waste product formed from the normal breakdown of muscles in the body. Creatinine is almost completely excreted by the kidneys, so their levels in the blood serve as an indication of kidney function.

Excess creatinine in the blood can be found due to decreased elimination from the kidneys as well as due to increased creatinine production by muscular breakdown, eating cooked meat, protein supplements, etc.

·         BUN/Creatinine Ratio:

BUN/Creatinine Ratio compares the levels of nitrogen as urea in blood to the levels of creatinine in the blood. This ratio serves as a more accurate representation of kidney function. It is also used to check for dehydration since the BUN level increases in dehydration while creatinine levels remain the same. Low BUN to creatinine ratio can be caused due to a low protein diet, liver cirrhosis, rhabdomyolysis (muscle disease), syndrome of inappropriate antidiuretic hormone secretion (SIADH) as well as during pregnancy.

Interpreting KFT results


Normal levels:

·         Urea:

2.5-7.8 mmol/L

 ·        BUN:

7 to 20 mg/dL

·         Uric Acid:

Adult Female: 2.4 to 6.0 mg/dL

Adult Male: 3.4 to 7.0 mg/dL

Children: 3 to 4 mg/dL

·         Creatinine:

Adult males: 0.6 to 1.2 mg/dL

Adult females: 0.5 to 1.1 mg/dL

·         BUN/Creatinine Ratio:

          12:1 to 20:1

Increased levels of each of these parameters can indicate a number of conditions and not necessarily health disorders. For example, increased creatinine levels can occur due to heavy exercise, consumption of cooked meat, or taking protein supplements apart from kidney diseases. Thus, these parameters are also considered while interpreting the tests. Further tests are performed to confirm any health disorders.

Answers to Patient Concerns & Frequently Asked Questions (FAQs) about KFT

Frequently Asked Questions about Kidney Function Test

Q. How is this test performed?
This test is performed on a blood sample. A syringe with a fine needle is used to withdraw blood from a blood vessel in your arm. The healthcare provider will tie an elastic band around your arm to make the blood vessels swell with blood. This makes it easier to withdraw blood. You may be asked to tightly clench your fist. Once the veins are clearly visible, the area is cleaned with an antiseptic solution and then the needle is inserted into the blood vessel to collect the sample. You will feel a tiny pinprick during the procedure. Blood sample once collected will then be sent to the laboratory.
Q. Is there any risk associated with this test?
There is no risk associated with the test. However, since this test involves a needle prick to withdraw the blood sample, in very rare cases, a patient may experience increased bleeding, hematoma formation (blood collection under the skin), bruising or infection at the site of needle prick.
Q. Is there any preparation required before the KFT test?
A fasting period of 8 to 12 hours is prescribed before the test is performed. Inform the doctor of any medications you may be taking. No other specific preparations are usually required before the Kidney Function Test.
Q. What additional tests can be prescribed by your doctor in case of abnormal KFT test result?
Additional tests that may be prescribed in case of abnormal Kidney Function test result are: · Blood Electrolyte Tests · Urine Creatinine Test · Estimated Glomerular Filtration Rate (eGFR) Test · Creatinine Clearance Test · Urinalysis · Blood Sugar Tests · Urine Albumin Test · Kidney Biopsy · Imaging Tests
Q. What is Chronic Kidney Disease (CKD)?
Chronic Kidney Disease (CKD) or Chronic Kidney Failure is a medical condition characterized by the steady and progressive loss of proper kidney functioning leading to complete kidney failure if left untreated. The kidneys filter out metabolic wastes out of the blood for excretion, and their progressive loss of function due to CKD causes these wastes to build up in the body to toxic levels. This may turn fatal in end stage kidney failure. CKD may be caused by conditions that affect kidney function, including: · Diabetes Type 1 and 2 · Hypertension (high blood pressure) · Glomerulonephritis (inflammation of the filtering units of the kidneys called glomeruli) · Interstitial nephritis (inflammation of the tubules of the kidneys) · Polycystic kidney disease (formation of cysts in the kidneys) · Urinary tract blockage due to kidney stones, prostate gland enlargement, or some cancers · Vesicoureteral reflux (backward flow of urine into the kidneys) · Pyelonephritis (general kidney infection) Symptoms of CKD are not easily apparent in the early stages. They build up in number and intensity as the disease worsens, usually only when significant damage has already occurred.
Q. What are the common symptoms of kidney disease?
Common signs and symptoms of kidney diseases include: · Swelling of the lower limbs, ankles, thighs · Puffiness around the face and eyes or in the wrists and stomach · Frothy or dark coloured urine · Blood in urine · Reduced urine volume · Burning sensation during urination · Change in frequency of urination · Pain in the mid back region below the ribs at the location of the kidneys
Q. What are the common risk factors for development of kidney diseases?
Common risk factors that may lead to development of kidney diseases include: · Diabetes · Hypertension (high blood pressure) · Heart and cardiovascular diseases · Family history of kidney diseases
+ more

Tests Included (4 tests)

  • BUN/Creatinine Ratio
  • Uric Acid
  • Creatinine
  • Urea/ Blood Urea Nitrogen



For over a hundred years, human pathology has been one of the keystones of medicine and rightly so at SRL, we offer our patients world-class Pathology services because their well-being is of the utmost importance to us. Pathology is quite simply the scientific study of the overall response of your body to any foreign influence, i.e., disease. Actually, we use this knowledge to diagnose & subsequently treat your ailment. What we basically do is carefully compare the normal structure and function...
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