Tests for kidney disease

Kidney disease often progresses silently, with no symptoms until a lot of harm has already been done. This makes testing important, especially if you're at increased risk due to factors like diabetes, high blood pressure, or a family history of kidney disease. Early detection and treatment can slow or even stop kidney disease from getting worse.

Learning about the tests available, what they do and what to expect can help you and your doctor catch kidney disease early when it is most treatable. Doctors can help find the cause of kidney disease through these tests, make a personalized treatment plan for your needs, and help you improve your quality of life.

Download our tests for kidney health printable guide

Blood tests

Blood tests can look for and measure substances (such as antibodies or proteins) that are signs of other health problems that may cause kidney disease, such as lupus.  

eGFR test (Estimated Glomerular Filtration Rate) 

eGFR (estimated glomerular filtration rate) is a measure of how well your kidneys are working. Your eGFR is an estimated number based on a blood test and your age, sex, and body type.

eGFR is considered a mostly reliable test for doctors to know how well your kidneys are working. However, the eGFR may not be accurate if you are younger than 18, pregnant, very overweight or very muscular. In addition, other tests such as  an ultrasound or a kidney biopsy may be ordered to find a cause of your kidney disease.

Serum creatinine test

Creatinine is a waste product in your blood that comes from your muscles. Healthy kidneys filter creatinine out of your blood through your urine.

Your serum creatinine level is based on a blood test that measures the amount of creatinine in your blood. It tells how well your kidneys are working. When your kidneys are not working well, your serum creatinine level goes up.

Your doctor can also measure creatinine with a urine test.

Blood urea nitrogen (BUN) test

Your blood urea nitrogen (BUN) level is based on a blood test that measures the amount of urea nitrogen in your blood. Urea nitrogen is a waste product that your body makes after it breaks down protein. Healthy kidneys take urea nitrogen out of your blood. When your kidneys are not working well, your BUN level goes up.

Cystatin C Test

The cystatin C test is a type of blood test to see how well your kidneys are working.  

Usually, to measure how well your kidneys are working, doctors check your eGFR (estimated glomerular filtration rate) by using a blood test for creatinine (a waste product made by your body's muscles). The eGFR is an estimated number to tell doctors what stage of kidney disease you have.  

Sometimes doctors may use the cystatin C test to check your eGFR if:  

• Past kidney function test results have come back unclear  
• Your creatinine levels are likely to vary for other reasons, such as older age or having a lot of muscle mass, like a body builder 

Urine tests

A urine test is when a doctor examines a small amount of your urine (pee) to check for signs of kidney disease and other health problems. When your kidneys are damaged, they may let protein leak into your urine. This can be one of the earliest signs of kidney disease.

Urine tests help your doctor: 

• Measure your kidney function 
• Find out what stage of kidney disease you are in
• Keep track of health problems that can cause kidney disease, such as diabetes
• Check for complications (problems) from kidney disease such as anemia and metabolic acidosis 
• Check for other problems such as a kidney infection or a urinary tract infection (UTI)

Albumin-to-creatinine ratio (UACR) 

The UACR is a simple urine test: 

1. You will give a small sample of urine (about two tablespoons). 
2. Your urine sample is sent to a lab to see the amount of albumin (the main protein in your blood) and creatinine (a waste product in your blood that comes from your muscles). 
3. Your doctor will compare these levels to figure out your UACR. 

If your UACR is more than 30 mg/g, ask your doctor when you should get the test again.  

24-hour urine test 

To do this test, your doctor will give you one or two large containers to collect your urine over a 24-hour period. They will also give you a special pan that fits in your toilet or a urinal to collect your urine. You will then transfer your urine from the pan to the container. Here is a sample of what you might do: 

1. When you first wake up, you will flush your urine from your first time urinating. 
2. Then, you will start collecting your urine–for the next 24-hours, you will collect all urine in the pan and container (you will not flush any urine down the toilet during this time). 
3. After 24 hours, you will bring it to a lab. The lab will test your urine for: 

• How much urine you make in a day 
• The acidity (how much acid is in your urine) 
• The amount of certain substances, such as: 
  • Protein 
  • Creatinine 
  • Calcium 
  • Sodium 
  • Uric acid 
  • Oxalate 
  • Citrate 

Ask your doctor how often you should have this test. 

Imaging tests 

Imaging tests look for physical changes in your kidneys that may help find the cause of your kidney disease, such as:  

• Abnormal size or shape of your kidneys 
• Blood flow to your kidneys 
• Signs of injury or damage to your kidneys 
• Kidney stones, cysts (fluid-filled sacs) or tumors 
• Size of or problems with your bladder (the organ that stores urine before it leaves your body) 

After an imaging test, a radiologist (a doctor specially trained in reading scan images) will read your images and give the results to your doctor. You and your doctor will go over the results and decide your next steps.  

Kidney ultrasound 

A kidney ultrasound (also called a renal ultrasound) is a safe and painless imaging test that uses sound waves to make pictures of your kidney: 

1. You will lie down on an exam table. 
2. The ultrasound tech (the person doing the ultrasound) will spread a warm gel on your belly over your kidney area.  
3. The tech will rub a small probe against your skin. 
4. The tech may ask you to hold your breath or roll on your side while the computer is measuring the sound waves as they bounce back from your body to create images. 

A kidney ultrasound takes about 20-30 minutes.  

Computed tomography (CT or CAT) scan of the kidneys 

A CT or CAT scan is a painless test that uses X-rays and computer technology to create detailed images of your kidneys: 

1. If you have a scan with contrast, you will get the contrast (a substance you will drink or get through a needle in a vein that helps certain tissues show up more clearly). 
2. You will lie down on an exam table that slides into a large, circle opening of a scan machine. 
3. The tech will move to another room to control the scan. You will be able to talk with the tech through a speaker system. 
4. The scanner will rotate around you, and you will hear clicking sounds. You will need to lie very still, and the tech may ask you to hold your breath. 
5. If you got contrast in a vein, the tech will remove it after the scan.  

A CT scan takes about 30 to 60 minutes.  

Magnetic resonance imaging (MRI) of the kidneys 

An MRI uses magnets and radio waves to make 3D (3-dimensional) pictures of your kidneys: 

1. You will lie down on an exam table that slides into a large tunnel-like tube in the scanner. 
2. The tech will move to another room to control the scan. You will be able to talk with the tech through a speaker system. 
3. The scanner will take many sets of images. You will hear loud noises coming from the scanner. 

An MRI takes about 30 to 60 minutes. 

Kidney biopsy

A kidney biopsy can help your doctor figure out what is causing your kidney problem, how severe your kidney problem is and the best treatment. 

Your doctor may suggest a kidney biopsy if tests show:

• Blood in your urine (hematuria) 
• Protein in your urine (proteinuria)
• Kidney disease with no clear cause
• Nephrotic syndrome (a group of symptoms that when happen together can show that your kidneys are not working as well as they should)
• Concern for glomerular or inflammatory kidney disease

Your doctor may also suggest a kidney biopsy to find out if:

• The treatment for your kidney problem is working
• There is damage to your kidneys that cannot be reversed
• A transplanted kidney is not working well
• You have a kidney tumor
• If your kidney problem is caused by a rare kidney disease 

If you have any questions about why you need a kidney biopsy and how it could help treat your kidney problem, talk to your doctor. 

Learn more about a kidney biopsy.

Genetic Testing

Genetic testing is a type of medical test that looks at your DNA, the genetic code that is unique to every individual.  

This testing uses a blood or saliva (spit) sample to look at changes in your genes, chromosomes or proteins. Genes are the information inside your cells that instruct it to do certain tasks, chromosomes are structures within your body's cells that contain your genes, and proteins are built from the cells using instructions found in your genes. Changes, or mutations, in your genes may cause certain types of kidney disease.  

Results from a genetic test can help doctors confirm or rule out a genetic condition or can help a person better understand their chances of developing or passing on a genetic disorder.  

Genetic testing may help your healthcare team to diagnose, monitor and manage certain types of kidney diseases. This type of testing can be helpful if you have a family history of kidney disease or if you don't know the cause of your kidney disease.  

You may want to consider working with a genetic counselor before or after genetic testing. They can tell you what test results mean and help support you and your family to make decisions based on your genetic testing results and offer helpful information to your healthcare team.   

How much does it cost for a kidney test?

The costs of these tests depend on your insurance coverage. Call your insurance company and ask if they cover a test and how much you may have to pay. If your insurance will not cover a test, there may be programs to help you pay.  

Ask your doctor to speak with a social worker or financial counselor for help with insurance and paying for tests.