What is kidney function test?

What is a kidney function test?

Kidneys help in the removal of waste products from the body. Excess fluids, salts, minerals, and other toxic substances removal are done by the kidneys in the urine. Blood and urine tests – kidney function test depict that how efficiently the kidneys are doing their job of the removal of the waste from the body.

Urine tests can show the presence of any abnormal leakage of albumin protein by the kidneys into the urine. A quick glance over the few tests done under the kidney function test (KFT) is discussed below in this article. Kidney disease can come as a disaster for anyone in the life all of a sudden. However, if the kidney disease is diagnosed early at its initial stages the chances of its reversal and recovery are more in comparison to the ones whose diagnosis occurs in the later stages.

Blood tests done at regular intervals for a healthy body checkup might make one aware of a newly occurring renal disease. If the treatment of disease is done on right time than damage reversal is possible. Like in acute renal injury reversal is possible if treated on time unlike in the case of chronic renal failure in which damage done cannot be reversed. So it is better to know your kidney numbers.

It includes mainly the two tests:

  1. Albumin to creatinine ratio (ACR): It shows the presence or absence of kidney disease by its values.
  2. Glomerular filtration rate (GFR): It further shows the stage of the kidney disease out of the 5 stages.


What is the reason for this test?


Several diseases like acute renal injury, chronic renal failure, nephritis, and glomerulonephritis etc. affect and alters the functioning of the kidneys. By detailed blood and urine analysis done under the KFT depicts the lab details by which diagnosis of the disease can be confirmed even its stage is also identifiable.


What are the different types of this test?


Urine Tests:

Albumin-creatinine ratio (ACR):

Urine evaluation, done for the presence of a protein known as albumin. Its presence in urine instead of blood reveals kidneys are not doing the filtration process properly. It is an early sign of a kidney disease. After this test comes positive further test, repeated for three positive results in a period of three months to confirm the presence of a kidney disease.

kidney function test


It involves microscopic examination of the urine sample along with the dip stick test reveals the presence of protein, blood, pus, bacteria, and sugar. It further helps in detecting the variety of kidney and urinary tract disorders like kidney stones, diabetes, bladder infections, and chronic kidney disease.

Creatinine clearance:

It compares the creatinine in a 24-hour urine sample to the creatinine level in the blood to reveal how much waste are the kidneys filtering per minute.

Blood Tests:

Glomerular filtration rate or GFR: 

In this test, the blood evaluation, done for the presence of a waste product called creatinine. It usually comes from the muscle tissue due to wear and tear of it. In case of damaged kidneys, there occurs trouble in removing creatinine from the blood. Identified value of creatinine, placed in a mathematical formula as per age, race, and sex to find the GFR.

Your GFR number reveals how well your kidneys, working and it is easily, analyzed by the specialist. A normal GFR value is 90 and above. For a GFR value – 60 it indicates kidney malfunction and – 15 indicates a risk of kidney failure and a need for transplant or dialysis. For a GFR test please reach out to your doctor.

Serum creatinine:

Its value in the blood can vary as per age, race, and sex. A creatinine level – 1.2 for women and -1.4 for men can be an early sign of the kidney disease. As the disease progresses its level in blood increases.

Blood urea nitrogen (BUN):

Breakdown of protein leads to urea nitrogen. The normal range of BUN is between 7 and 20. As kidney function decreases the BUN level raises.

Imaging or scanning:

Following tests – done in this for confirming kidney disease presence:


In this sound waves, used to obtain a picture of the kidney. Small abnormalities of size and position in the kidneys, seen in this like stones and tumors.

kidney function test

Computerized tomography scan or CT scan:

In this image of the kidneys, created using X-rays. It helps in identifying any structural abnormalities or obstructions. In this intravenous contrast dye, used to identify the damage caused by the kidney disease.

Kidney biopsy:

A biopsy, done with the help of a thin needle. A thin needle, inserted with a sharp cutting edge to slice small pieces of the kidney tissue. The examination of the small pieces, further done under the microscope.

It is occasionally because of the following reason:

  • To detect a specific disease and evaluate if it responds to the treatment or not
  • Detect the reason of kidney transplant failure
  • To evaluate the amount of damage done to the kidneys


The kidney function tests mainly blood and urine analysis help in identifying any kidney abnormalities in the initial stages. Further, this helps in knowing about kidney disease early and proper treatment can reverse the disease. A person can achieve the pre-disease efficient kidneys after complete reversal by proper therapy.

Therefore, regular health checkups are must in the current era where endless diseases are around and the only way of early detection is awareness and lab results. This helps in dealing with all the kidney diseases as early as possible with the best possible treatments.

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