Kidney Function Test: Everything You Need To Know

What Is A Kidney Function Test?

You have two kidneys, one on each side of your spine, each about the size of a human fist. They are located beneath your rib cage and posterior to your abdomen. Your kidneys play several essential roles in your overall health. One of their most important functions is to filter waste materials from the blood and expel them as urine from the body. The kidneys also aid in the regulation of the body’s water and mineral levels. Furthermore, they help to produce vitamin D, red blood cells, and blood pressure-regulating hormones.

Kidney function tests are simple procedures that use either blood or urine to help diagnose kidney problems. There are several types of kidney function tests that look into different aspects of kidney function. A kidney function test may get performed to determine whether the kidneys are filtering waste products too slowly. Another type of test may get performed to determine whether the kidneys are leaking proteins into the urine.

If your doctor suspects that your kidneys aren’t working well, you may require kidney function tests. If you have other conditions that can harm your kidneys, such as diabetes or high blood pressure, you may also require kidney function testing. They can assist doctors in monitoring these conditions.

You can learn about a variety of kidney function tests and their outcomes in this article.

Types Of Kidney Function Tests

Your doctor will order a series of tests to assess your kidney function and estimate your glomerular filtration rate (GFR). Your GFR informs your doctor about how quickly your kidneys remove waste from your body. Wastes and excess fluid are removed from the blood by healthy kidneys. Blood and urine tests show how well the kidneys perform their functions and how quickly wastes get removed from the body. Urine tests can also detect if the kidneys are leaking excessive amounts of protein, which is a sign of kidney damage.

Here’s a rundown of the tests used to assess kidney function.

  • Blood Tests
  • Imaging Tests
  • Kidney Biopsy
  • Urine Tests

Below is a detailed account of the tests conducted to check your kidney function.

Blood Tests
Serum Creatinine Creatinine is a waste product produced by the body's muscles due to normal wear and tear. Creatinine levels in the blood vary with age, race, and body size. A creatinine level of more than 1.2 and 1.4 for women and men, respectively, may indicate that the kidneys are not functioning well. Creatinine levels in the blood rise as kidney disease progresses.

Glomerular Filtration Rate(GFR)

(mathematical formula using the MDRD or CKD-EPI equation)

This test determines how well the kidneys remove wastes and excess fluid from the blood. It gets calculated using the serum creatinine level, age, and gender, adjusting for African American descent people. Normal GFR can vary with age (as you grow in age, it can decrease). If GFR remains 90 or higher, then it gets considered normal. A GFR less than 60 indicates that the kidneys are not working adequately. Once the GFR falls below 15, the patient is at high risk of needing kidney failure treatment, such as dialysis or a kidney transplant.
Blood Urea Nitrogen (BUN) The breakdown of protein in the foods you eat produces urea nitrogen. The standard BUN level ranges between 7 and 20. The BUN level rises as kidney function declines.
Imaging Tests
Ultrasound This test employs sound waves to create an image of the kidney. Whether it detects changes in the size or position of the kidneys; any obstructions such as stones or tumors, the doctors can use this test to assess the condition of the kidneys.
CT Scan The kidneys get imaged using X-rays in this imaging technique. A CT scan can also detect structural irregularities and the presence of obstructions. This test may necessitate using intravenous contrast dye. But, it might be dangerous for people with kidney disease.
Kidney Biopsy

A biopsy may get performed on occasion for one of the following reasons:

  • to identify a specific ailment process and determine whether it will respond to a particular treatment
  • to assess the amount of harm that has occurred in the kidney
  • to determine why a kidney transplant may be failing

A kidney biopsy gets performed by slicing tiny pieces of kidney tissue using a thin needle with a sharp cutting edge, which the doctor can examine under a microscope.

Urine Tests
Some urine tests need only a few tablespoons to get accurate results. Other tests necessitate the collection of all urine produced over 24 hours. A 24-hour urine test helps measure the amount of urine your kidneys create, thus providing a more accurate measurement of the functioning of your kidneys and how much protein leaks into the urine in one day.
Urinalysis A microscopic examination of a urine sample, as well as a dipstick test, are included. The dipstick consists of a chemically treated strip that gets dipped into a urine sample. When abnormalities such as excess protein, blood, pus, bacteria, or sugar are present, the strip changes color. A urinalysis can aid in the diagnosis of several kidneys and urinary tract disorders, such as chronic kidney disease, diabetes, bladder infections, and kidney stones.
Urine Protein It can be done as part of urinalysis or separately with a dipstick test. Proteinuria gets defined as an excess of protein in the urine. A positive dipstick test (1+ or higher) should get confirmed with a more specific dipstick test. It could include an albumin-specific dipstick or a quantitative measurement, such as an albumin-to-creatinine ratio.
Microalbuminuria It is a more sensitive dipstick test that can detect a trace amount of albumin in the urine. If a standard dipstick test for proteinuria is negative, people at a higher risk of developing kidney diseases should have this test or an albumin-to-creatinine ratio.
Creatinine Clearance Creatinine is a waste product produced by the body's muscles due to normal wear and tear. The creatinine clearance test compares the creatinine level in your blood to the creatinine level in a 24-hour urine sample to determine how much waste products your kidneys filter out each minute.

Kidney Function Test: What Is It Used For?

A kidney function test may get used as part of a general health screening. It can aid in the diagnosis and management of kidney-related conditions, screen someone at risk of developing kidney disease or follow someone with known kidney disease.

When a person has risk factors for kidney dysfunction, such as high blood pressure (hypertension), diabetes, cardiovascular disease, obesity, elevated cholesterol, or a family history of kidney disease, a healthcare practitioner may order a renal panel. Although early kidney disease frequently does not manifest any symptoms, it can get detected through routine blood or urine testing. Some signs and symptoms are as follows:

  • Puffiness or swelling, particularly around the eyes or in the face, wrists, stomach, thighs, or ankles
  • Foamy, bloody, or coffee-colored urine
  • a reduction in the amount of urine
  • Urinary problems, such as a burning sensation or abnormal discharge during urination, or a change in urination frequency, particularly at night
  • Pain in the mid-back, below the ribs, near the kidneys

What Is The Kidney Function Test Procedure?

Kidney disease can strike anyone at any time. If kidney disease is detected and treated early, you can help slow or even stop its progression. The majority of people with early kidney disease have no symptoms. It is why it is critical to get tested. A 24-hour urine sample and a blood test usually are required for kidney function tests.

Kidney Function Test Procedure For 24-Hour Urine Sample

A creatinine clearance test gets performed using a 24-hour urine sample. It tells your doctor the creatinine your body excretes in a single day.

  • Urinate into the toilet as you normally would when you wake up on the day you begin the test.
  • Urinate into a separate container provided by your doctor for the rest of the day and night.
  • During the collection process, keep the container capped and refrigerated.
  • Ensure that you clearly label the container and explain why it’s in the refrigerator to other family members.
  • When you wake up on the second day, urinate into the container. It concludes the 24-hour collection period.

Follow your doctor’s instructions on where to deliver the sample. You may be required to return it to your doctor’s office or a laboratory.

Kidney Function Test Procedure For Blood Samples

BUN and serum creatinine tests necessitate the collection of blood samples in a lab or doctor’s office.

  • The technician who will be drawing your blood first wraps an elastic band around your upper arm. It draws attention to the veins.
  • After that, the technician cleans the area around the vein. They insert a hollow needle into your vein through your skin.
  • The blood will be drawn back into a test tube and sent for analysis.
  • When the needle enters your arm, you may feel a sharp pinch or prick. Following the test, the technician will apply gauze and a bandage to the puncture site.

Over the next few days, the area around the puncture may bruise. You should not, however, experience severe or long-term pain.

Preparation For A Kidney Function Test

Usually, for a kidney function test that uses blood samples, your healthcare practitioner or doctor may ask you to fast overnight to prepare you for the test. In the case of a urine sample, it might require you to collect it in a separate container. Either for 24-hours periodically or once on the day of the test.

But, when it comes to imaging tests for kidney functioning, the preparation will depend on the type of procedure your doctor has ordered.

Before The Test
Some things you may need to do to prepare for your ultrasound include:

  • Drinking a quart of water before the test to improve image quality
  • The night before the test, eat a low-fat dinner
  • Fasting is a type of fasting (limiting or avoiding food for some time)

You may not need to do anything before your ultrasound in some cases. Your doctor will tell you precisely what you need to do before the test. If you have any questions about how to prepare for your ultrasound appointment, contact your provider’s office.

During The Test
During your imaging test, you will get asked to lie on an examination table. The ultrasound technician will apply a warm, water-soluble gel to your skin over the area getting examined. This gel will not irritate your skin or stain your clothes. After that, a probe gets gently placed against your skin. During the test, you may get asked to hold your breath or roll on your side several times. The ultrasound usually takes 20 to 30 minutes to complete.

After The Test
Monday through Friday, the results of your ultrasound are usually available within 24 hours of the test. Typically, the test results will be discussed with you by the healthcare provider who ordered the test.


Kidney Function Test Results Explained

Kidney function tests might be for several reasons, including a yearly checkup or if a urinary tract infection is suspected. They may also get performed if a person is sick, but no diagnosis has been made, as a screening test for a patient preparing for or recovering from surgery to track kidney disease.

Kidney function tests are a credible way of assessing the kidneys, but they can also change significantly with illness or dehydration. Many people can have an acute (temporary) kidney problem that resolves after receiving fluids or other treatment. There are numerous kidney function tests available, but only a few produce reliable results – the ones listed below.

Serum Creatinine Normal Lab Values:
Men: 0.7-1.3mg/dL
Women: 0.6-1.1 mg/dL
Estimated Glomerular Filtration Rate (GFR) Normal Lab Value:
90-120 ml/minute

Problem Value:
60 ml/minute or less indicates kidney damage may be present
Blood Urea Nitrogen (BUN) Test Normal Lab Value:
7-21 mg/dL

Who Should Get A Kidney Function Test?

If your doctor suspects that your kidneys aren’t working well, you may require kidney function tests. These are simple blood and urine tests that can detect kidney problems. If you have other conditions that can harm your kidneys, such as diabetes or high blood pressure, you may also require kidney function testing. They can assist doctors in monitoring these conditions. The following symptoms may indicate a kidney problem:

  • blood in the urine
  • high blood pressure
  • frequent urges to urinate
  • difficulty starting urination
  • painful urination
  • swelling of the hands and feet as a result of a fluid buildup in the body

A single symptom does not always indicate a grave problem. When these symptoms occur at the same time, it shows that your kidneys aren’t working well. Kidney function tests can assist in determining the cause.

How Much Does The Kidney Function Test Cost?

While you cannot predict the cost of kidney function tests, it gets determined by the number of tests ordered by your doctor. If you only need basic tests for kidney function, the cost may be lower. However, if the doctor directs a battery of tests, the price will rise proportionally.

Typically, the kidney function test cost is reasonable and will provide you with the results you require without costing you an arm and a leg. However, only your doctor can determine how many tests you need. So, if you notice any of the symptoms of irregular kidney function, consult your doctor and seek the appropriate treatment for your health problem.

How Often Should I Have A Kidney Function Test?

You can either go for an annual check-up to test your kidney function. Or, if you have any underlying health issues like high blood pressure or diabetes, your doctor may advise you to get your kidneys tested more often.

In a nutshell, the number of times you might have to take the kidney test depends on your overall health. If your doctor indicates that you may have symptoms of kidney disease, they will order a series of tests to ensure you get the correct treatment at the right time.

Kidney Function Test: Related FAQs

When it comes to any health issue, most people have questions and concerns that need addressing. Below you will find the answers to the most frequently asked questions related to kidney function tests that might have crossed your mind as well.

Q1. Is fasting necessary for kidney function test?
Typically, for blood tests ordered for kidney function, you will need to fast for at least 8-12 hours before your test. However, other kidney function tests like ultrasound and urine tests may not require you to fast beforehand. But, whether you need to fast or not depends on your doctor and his assessment of your condition. Therefore, consult a certified healthcare practitioner before you go for your kidney function test.

Q2. What should I avoid before a kidney function test?
When your doctor prescribes a kidney function test, they will mention the dos and don’ts before your test. Whether it is fasting or eating specific foods, they will address everything you need to know before the test. So, speak with your healthcare provider to learn about things to do and things to avoid before your kidney function test.

Q3. Can kidney function test results be wrong?
Almost all kidney function tests give accurate results. Depending on the test ordered by your doctor, you can get yourself tested and share the findings with them to get an extensive analysis. Your doctor remains the best judge of which tests you need to undergo, and therefore if you happen to get a kidney function test, your results will more often than not give the right results.

Q4. How to test kidney function at home?
You will find many labs that offer blood sample collection at home. So, if you need to get the kidney function test, as directed by your doctor, you can get in touch with a certified and well-reputed diagnostic lab that provides this facility. Alternatively, you can call upon your doctor to check if they can direct you to the concerned healthcare provider, where you can avail of this facility.

Q5. What is the normal kidney function level?
As per the serum creatinine test, your normal kidney function value should range between 0.7 and 1.3 mg/dL for men and 0.6 and 1.1 mg/dL for women. The estimated glomerular filtration rate (GFR) normal value lies between 90 and 120 ml/minute. On the other hand, the BUN value for your kidney to function well should remain in the range of 7 and 21 mg/dL.

Q6. What is the most important test for kidney function?
Both blood tests and urine tests give an accurate assessment of your kidney function. However, other tests like ultrasound and CT scans may also yield good results. But, which kidney function test is necessary for you remains in the hands of your doctor. Therefore, get yourself tested only on the recommendation of a certified healthcare practitioner.

Q7. What are the signs that something is wrong with your kidneys?
The signs and symptoms of kidney disease or failure include blood in the urine, high blood pressure, and frequent urination. They also cover difficulty urinating and swelling of your hands and feet due to fluid build-up. Sometimes, you may not notice any signs or symptoms of kidney disease, which is why getting your kidneys tested regularly is the way forward.


Kidney function tests are an essential part of diagnosing and treating kidney disorders. Even if a person does not yet have symptoms, they may need to get tested regularly. Experts recommend that people who are at a higher risk of kidney problems have regular kidney function tests. Those at graver risk include those who have:

  • Diabetes
  • Heart disease
  • High blood pressure
  • a history of kidney disease or failure in the family

Regular kidney function tests can assist in detecting kidney problems early and when the prognosis is favorable.

You can help prevent the progression of the condition by adhering to a treatment plan. The best way to monitor and manage any signs of kidney damage or underlying conditions is to work directly with a doctor.

Why Should You Reach Out To Aims Healthcare For Your Kidney Function Tests?

In today’s world, going to the hospital to take any test can be dangerous. Aims Healthcare’s Lab at Home service in Dubai, on the other hand, allows you to take the test in the comfort of your own home, office, or even hotel.Our DHA-licensed nurses and expert lab technicians will arrive at your doorstep within 30 minutes to take your blood sample. Moreover, we make the best healthcare professionals accessible and just one call away. So, to receive personalized medical care exclusively at your doorstep 24×7 and 365 days, Get in touch at +971 458 26 555 or fill out the contact form for more information.

Aims Healthcare

Aims Healthcare intertwines superior medical practices with accessibility of highly qualified medical professionals to yield exceptional patient care and clinical outcomes. We take medical care one step further by providing first-rate home healthcare and doctor-on-call services at your doorstep. We are available any time of day for you and every member of your family.