What Are Kidney Function Tests?
Kidney and Urologic Diseases Data Verified

Kidney Function Tests - Testing the Working Efficiency of Kidneys

Published on Jan 27, 2023   -  4 min read


A kidney function test is mainly done to determine the kidneys' efficiency. This article describes in detail the kidney function test.

What Is a Kidney Function Test?

As the name suggests, kidney function tests are done to assess the functionality of the kidneys. In simple terms, these are a series of tests to evaluate how well the renal system or the kidneys function. Most kidney function tests measure the glomerular filtration rate. The glomerular filtration rate mainly measures the kidney's capacity to filter blood and remove toxins from the body. A kidney function might comprise a blood test or a 24-hour urine collection test. The test results are usually available the same day or a few days after the procedure.

What Are the Functions of the Kidney?

The kidneys are integral urologic organs of the body as they help the body get rid of waste in the form of urine. They are usually present below the spine on either side of the rib cage. The kidneys contain a network or a tuft of blood vessels known as the glomerulus. The main function of the glomerulus is to remove toxins and return useful products to the bloodstream. The other functions of the kidneys are listed below:

  1. Regulate the electrolyte levels of the body.

  2. Control the production of red blood cells.

  3. Maintain the vitamin D levels in the body.

  4. Synthesize the hormones that regulate the blood pressure of the body.

What Are Some of the Signs and Symptoms of Kidney Problems?

Sometimes, the patient has an underlying renal problem but remains asymptomatic for prolonged periods. However, the problem arises when the medical condition goes unnoticed, exacerbating the symptoms. The following symptoms indicate that there are some problems with the kidneys:

Why Would a Patient Need to Undergo a Kidney Function Test?

A kidney function test is done to gain insight into the kidneys. This is because conditions like diabetes and hypertension affect the working of the kidneys. Patients with these conditions might require a kidney function test to monitor their condition. The patient usually requires a kidney function test if he experiences the following:

  1. Microscopic or macroscopic hematuria.

  2. Dysuria (painful urination).

  3. A strong urge to urinate, but the urine does not pass.

  4. Problems in starting the urine stream.

What Are the Different Types of Kidney Function Tests?

The doctor might order one or more types of kidney function tests to determine the condition's exact cause. The different types of kidney function tests are described below:

  1. Blood Urea Nitrogen Test (BUN) - As the name suggests, this test detects the quantity of urea nitrogen in the blood. Normally, the kidneys consider urea nitrogen as waste and remove it from the blood. In simple terms, urea nitrogen is formed due to the breakdown of proteins. In addition to kidney diseases, urea nitrogen levels can be elevated due to large doses of Aspirin and other antibiotics. The patient needs to inform the doctor about the vitamins and other herbal supplements he is taking to diagnose the probable causes of elevated BUN levels. The patient might be asked to stop taking the drugs before the test. Normally, the BUN levels range from 7 to 20 mg/dL. A higher value is usually related to a health condition.

  2. Urinalysis - A urinalysis is a screening test to detect the proteins and blood in the urine. Though proteins might be present in the urine due to several possible reasons, kidney disease remains the principal cause. Urinalysis can be easily done at home. The patient has to collect the urine sample and send it to the hospital for examination. The laboratory technician generates a report and sends the same to the examining doctor. After reviewing the test reports, the doctor might ask for a thorough medical history of the patient, including his daily activities. For example, people involved in sports activities and strenuous exercises usually demonstrate elevated protein levels in the blood.

  3. Serum Creatinine Test - It is a blood test examining the blood's buildup of creatinine. Normally, the kidneys completely remove creatinine from the blood. Creatinine is a waste product produced by the muscles after utilizing the energy. Studies report that creatinine levels of more than 1.2 mg per dL indicate kidney diseases.

  4. Estimated Glomerular Filtration Test - This test shows how well the kidneys filter the blood and remove the toxins. It determines the values by observing the following factors:

    1. Age.

    2. Height.

    3. Weight.

    4. Race.

    5. Gender.

    6. Test results.

What Happens in a Kidney Function Test?

A kidney function test usually requires blood and 24-hour urine collection tests. The tests are described below:

  • 24-Hour Urine Test - In this test, the patient collects the urine sample throughout the day in a container. The container is kept in a refrigerator until the next day. Finally, after 24 hours, it is sent to the laboratory. This test helps evaluate urea, creatinine, bacteria, white blood cells, and pus levels.

  • Blood Test - Serum creatinine and BUN tests are usually done with the help of a blood sample. A cuff or a band is tied around the patient’s arm to inject a small amount of blood. The technician collects the blood in a vacuum cleaner and examines it under the microscope. This test measures the creatinine and urea nitrogen levels in the blood.

What Happens After a Kidney Function Test?

Kidney function tests usually do not produce any complications or side effects. However, some patients might experience bruising, fatigue, and dizziness. Urine and blood tests do not cause any problems or long-term complications. The patient can consult his doctor if he experiences pain or other symptoms after the test.

How Is Early Kidney Disease Managed?

The doctor primarily focuses on managing the underlying condition if the patient is diagnosed with early kidney disease. The doctor might also prescribe medications to lower the patient's blood pressure. He might suggest dietary and lifestyle modifications in case of mild kidney disease. Diabetic patients might be referred to an endocrinologist (a doctor specializing in metabolic diseases and hormone-related disorders). The doctor might recommend painkillers if the patient experiences pain due to kidney stones, urinary tract infections, or other disorders.


A kidney function test helps the doctor evaluate multiple urologic conditions and their causes. It is preferred over other tests because it gives an idea about the patient's general health and kidney-related problems. So, people with kidney diseases and other underlying medical conditions must undergo this test after consulting their doctor.

Last reviewed at:
27 Jan 2023  -  4 min read




Comprehensive Medical Second Opinion.Submit your Case

Related Questions & Answers

What test should I do to know if I am HGH deficient?

Query: Dear doctor, I want to test myself for HGH deficiency. Can you tell me a complete guide on how should I proceed? What tests should I do? After I have done them, can I post it here for a thorough examination from your doctors, so that they can tell me whether I am HGH deficient? I want to test that...  Read Full »

Vitamin B12 level is high in a diabetic patient. Please help.

Query: Hello doctor, I am 60, weight is 44 kg, height is 5.6, diabetes for past 25 years, on low carbohydrate diet for 80 days, taking no medicine for diabetes now. Sugar levels are under control, checking every day. The problem from past 50 days is that there are feet and ankle swelling that disappears i...  Read Full »

What is the treatment for gynecomastia with increase in weight?

Query: Hi doctor, I am 18 years old. My weight is 176 lbs, and my height is 5.9 feet. I have gynecomastia for the past four years. Please recommend some medicines.  Read Full »

Popular Articles Most Popular Articles

Do you have a question on Kidney Function Test or ?

Ask a Doctor Online

* guaranteed answer within 4 hours.

Disclaimer: No content published on this website is intended to be a substitute for professional medical diagnosis, advice or treatment by a trained physician. Seek advice from your physician or other qualified healthcare providers with questions you may have regarding your symptoms and medical condition for a complete medical diagnosis. Do not delay or disregard seeking professional medical advice because of something you have read on this website. Read our Editorial Process to know how we create content for health articles and queries.