Kidney Function Test (KFT) Procedure, Types and Purpose

There are 2 kidneys on either side of your spine which are approximately the size of a fist. These are located posterior to the abdomen and below the rib cage. Kidneys play an important role in maintaining your health. The important job is to filter out the waste materials from the blood and take them out via the urine. The kidneys help to control the level of water present in the water. Kidneys are critical to the production of:

  • Red blood cells
  • Vitamin D
  • Hormones which regulate blood pressure

If your kidneys are not working well, then you might require a kidney function test as if you are suffering from high blood pressure or diabetes.

Also Read: Causes of Kidney Disease


Kidney Problems – Symptoms

Symptoms which indicate a problem with kidneys include:

  • Blood present in the urine
  • Urge to urinate
  • Pain while urinating
  • High blood pressure
  • Swelling of feet and hands due to the buildup of fluids in the body
  • Difficulty in starting urination

If you are having a single symptom, then it may not mean serious. But if the symptoms occur continuously, this suggests that your kidneys are not working properly. By the help of kidney function tests, you can determine the reason.

Kidney Function Tests – Types

To test the kidney function, the doctor will order some set of tests which will tell your glomerular filtration rate (GFR). The GFR tells how fast your kidneys are able to clear waste out from your body.


A urinalysis will tell you about the presence of blood and protein in your urine. There can be a number of reasons for protein in your urine, all of which aren’t related to the disease. Infection increases the protein in urine and if you are doing any heavy workout, this will also do the same. The doctor will repeat this test after some weeks to check the results. The doctor can ask you to provide 24-hour urine collection, this will help the doctors to see how fast a waste product creatinine is clearing out from the body.

Serum Creatinine Test

This blood test will tell whether creatinine is building up in the blood. The kidneys will filter creatinine from the blood. If your body has a high level of creatinine, it means you are suffering from a kidney problem. A creatinine level which is higher than 1.2 milligrams for women and 1.4 milligrams for men is a sure shot sign of a kidney issue.

Blood Urea Nitrogen

The blood urea nitrogen test checks for the waste products present in your blood. BUN tests will measure the amount of nitrogen present in the blood. Urea nitrogen is the breakdown product of protein. The common medications, which includes large doses of aspirin and some antibiotics which can increase your BUN. it’s necessary to tell your doctor about the medications you are taking regularly. You should stop taking drugs a few days before the test.

Also Read: Carbonated Beverages May Be Hurting Your Kidneys


How The Tests Are Done?

Kidney function tests require a 24-hour blood test and a urine sample.

24-hour urine sample

A 24-hour urine sample means a creatinine clearance test. It provides the doctor with an idea that how much creatinine your body takes out over a single day. On the day of the test, urinate to the toilet as you would normally do. For the rest of the day urinate into a special container which is provided by your doctor. On the second day, urinate into the container when you wake up. This will complete the 24-hour process.

Blood Samples

BUN requires blood samples to be taken in a lab. The technician will tie an elastic band around the upper arm. This will make the veins to appear. The technician will clean the area over the vein. He will put a hollow needle via your skin into the vein. The blood will flow back to a test tube which will be sent for analysis. You might feel a sharp pinch when the needle enters your arm. The area around the puncture might develop a bruise for some days.

Early Kidney Disease- Treatment

treatment for kidney stones

The doctor will focus on treating the condition if some tests show early kidney disease. The doctor will prescribe medications which will control the blood pressure if tests can indicate hypertension. The doctor will suggest lifestyle changes. If you are suffering from diabetes, the doctor might refer you to an endocrinologist. This doctor will specialize in metabolic diseases which can ensure that you can have the best blood glucose control. If there are other causes for abnormal kidney function tests, like kidney stones and the use of painkillers, the doctor can ta+ke great measures to manage the disorders.


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