Kidney Function Test

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WHAT IS KIDNEY FUNCTION TEST? Kidney function tests can be defined as simple procedures involving the use of either blood or urine or both in identifying abnormalities in the kidney.  The kidney is a small bean-shaped organ located in the abdomen and helps in the filtering of waste products from the body in the form… Read More

Kidney Function Test


Kidney function tests can be defined as simple procedures involving the use of either blood or urine or both in identifying abnormalities in the kidney. 

The kidney is a small bean-shaped organ located in the abdomen and helps in the filtering of waste products from the body in the form of urine. The kidney also plays an important role in maintaining the normal functioning of the body and damage to the kidney could affect the filtering of waste product from the body, resulting in an accumulation of waste in the body which could lead to serious complications in the body. The kidney is also vital in the production of vitamin D, red blood cells, hormones that regulate blood pressure.

According to the National Kidney Foundation, at least one in every three adults in the united states is at risk for kidney disease. Kidney disease hardly shows symptoms in its early stage hence it’s very important to undergo a kidney function test in other to prevent damage to the kidney.


Kidney function test targets screening the kidney for any damage to its functions and use for early diagnosis and treatment of kidney diseases resulting in proper care and halting any infection that may have been progressing in the kidney. 

This involves examining the rate of glomerular filtration rate as it shows how quickly or slowly the kidney is removing waste from the body.


A kidney function test is usually recommended by the doctor to examine your glomerular filtration rate. 

The following tests are how to test for kidney function:

  • Urine Test

The urine test is characterized by the use of a urine sample or all the urine produced by the body in 24hours. This process is called a urinalysis. It is used to identify particles in the urine such as blood, pus, bacteria, sugar, protein, etc, and when such particles are found in the urine it could indicate kidney or bladder infection, kidney stones, diabetes, etc. infections may increase urine protein.

  1. Microalbuminuria or Albumin to Creatine Ratio Tests 

This test involves the use of a urine sample and it is examined for albumin. Albumin is a protein that if found in the urine indicates that the kidney is filtering too much of it and hence there is damage to the kidney. 

In this kidney function test, normal levels of urine albumin results are 30milligrams per gram. 

After the kidney function test, a low or high level of albumin indicates the presence of kidney disease. This test is very sensitive and detects very minute particles in the urine.

  • Creatine Clearance Test

Creatine clearance test both a blood and urine test, this procedure involves collecting urine samples a person creates in 24 hours and also collecting blood samples. Creatine is a waste product produce by the muscles naturally from daily use. Then the result of the urine analysis and the blood test is compared and the level of creatine examined.

  • Serum Creatinine Test

A serum creatinine test is a blood test that examines creatinine build in the blood as the kidney normally filters a creatinine from the blood.

In this kidney function test, creatinine at a high level indicates kidney damage. 

The usual level of creatinine in the blood is 1.2 milligrams per deciliter for women and i.4 milligrams per deciliter for men anything higher than this could be an indication of an infection.

  • Blood Urea Nitrogen Test

Blood urea nitrogen test is used to examine the blood for waste such as urea, nitrogen which occurs as a proteinous breakdown of food. Hence, a rise in these may indicate kidney malfunctioning. The normal range of a blood urea nitrogen test is between 7-20 milligrams per deciliter. However, this test could be affected by medications such as antibiotics, food rich in protein, etc. when undergoing this test, inform your doctor about any medications you might be taking.

  • Estimated Glomerular Filtration Rate

This test aims at examining the rate at which the kidney is filtering waste from the body. When undergoing this test, certain factors are considered such as test results specifically creatinine level, age, gender, race, height, weight, etc. if the result is less than 60 millimeters per minute then it indicates kidney damage.

  • Kidney Biopsy

A kidney biopsy involves taking a sample from the kidney and taken to the lab for examining and the kidney cells are observed for any abnormality.

  1. Kidney Ultrasound   

A kidney function test could also involve an ultrasound scan called renal ultrasound. This scan gives a picture of the kidney through the use of sound waves.


A kidney function test is usually recommended by your doctor but it could also undergo such test if you suspect anyone with your kidney since most kidney diseases or infections hardly give signs or symptoms in their early stage.


When preparing for a kidney function test, avoid smoking and reduce your drinking of alcohol

Inform your doctor of any medications especially antibiotics you may be taking

Come with a friend for emotional support.


A kidney function test usually requires a 24-hour urine sample and blood sample which could be a creatinine clearance test, blood urine nitrogen, serum creatinine test, etc as this tends to give the doctor an idea of the level of creatinine your body expels in a day. 

You will be required to urinate as soon as you wake up into a special container for the rest of the day and night. You will have to keep the container closed and refrigerated during the process of collecting the sample. The container should be properly labeled and stored properly. After 24 hour period, you will have to take the sample back to the lab.

If it is a blood sample that is to be used, your sample will be collected by a lab technician by inserting a hollow needle through the vein and your blood is drawn and the sample taken into the lab.


In kidney function tests an increase in creatinine in the urine or blood shows an infection in the kidney. Also, a kidney function test screens the kidney for any particles such as pus, albumin, etc, as this indicates the malfunctioning of the kidney and the glomerular filtrate rate. 

After a kidney function test, the normal range of the estimated glomerular filtrate rate is about 100 millimeters per minute. When it is between the range of 59 – 29 millimeters per minute, there might be kidney damage and there is a need for immediate treatment.

Does This Test Requires Any Risk Or Side Effects?

Kidney function test does not involve any side effects apart from pains and bruises that may occur when a blood sample is being taken by the lab technician which clears within a day or two.


  • Is fasting required for kidney function tests?

When undergoing a kidney function test, it is not necessary to fast before undergoing a renal function test because they are not affected by the meals to any meaningful degree.

  • What is the best way to make sure the kidney is functioning properly?

There are simple habits that can be done to ensure that your kidney is functioning properly. They include keep active and exercise regularly, control your sugar level, monitor your blood level regularly, monitor your weight, try eating healthy, avoid smoking, have your kidney function tested if you have diabetes, high blood pressure, etc.

  • What is the most important test for kidney functioning?

The most important test for the kidney is the glomerular filtration rate  as it checks for chronic kidney disease and tells how well the kidney is functioning

  • What blood test shows kidney function?

Kidney function can be accurately tested using a blood urea nitrogen test that measures the level of creatinine and cystatin C in the blood 

  • Can you have kidney disease and not know it?

Most kidney diseases do not give signs at their inception and early stage, as a result, you may not know your kidney is damaged until the disease has become severe and the function of the kidney is lost.