Kidney disease hides in plain sight. You can’t feel it early, but you can find it early. The American Kidney Fund’s guidance highlights the tests that reveal the truth long before symptoms appear, and this guide explains each one.
Below is an overview of the major tests used to assess kidney health and what each can show.
What Your Kidneys Do
Your kidneys filter waste, balance minerals, support blood pressure, and help keep your blood and bones healthy. When they begin to struggle, the effects can spread through the body. Early testing can slow or even prevent long-term damage, especially if you have diabetes, high blood pressure, heart disease, or a family history of kidney problems.
Blood Tests
eGFR
The estimated glomerular filtration rate, or eGFR, is the main number doctors use to understand how well your kidneys are working. It shows how much blood your kidneys can filter in a minute. The calculation is based on your creatine level along with your age and sex.
Creatine is a waste product your muscles make throughout the day. With eGFR, higher numbers are better. Most adults look for a value of 60 or above. When eGFR stays below 60, doctors start checking more closely for signs of chronic kidney disease.
Cystatin C
Cystatin C is a protein your body makes, and your kidneys filter out. It is helpful when creatinine-based eGFR may not be accurate, such as in older adults or people with high muscle mass. A cystatin C-based eGFR can give a clearer picture of kidney function when results are uncertain.
Serum Creatinine
Creatinine is a waste product your muscles release into your blood. When your kidneys slow down, creatinine builds up, so higher levels can signal a problem. This test is simple and widely used, and it is most helpful when interpreted with eGFR.
Blood Urea Nitrogen (BUN)
BUN measures urea nitrogen, a waste product your body makes when it breaks down protein. Healthy kidneys remove it from the blood. BUN is useful, but not a standalone measure. Doctors interpret it alongside creatinine and eGFR to understand the full picture.
Urine Tests
Urinalysis
A basic urine test that checks for protein, blood, sugar, and signs of infection. It can reveal early kidney changes and other health issues.
Urine Albumin to Creatinine Ratio (uACR)
uACR is one of the most important tests for early kidney damage. It measures how much albumin, a protein that should stay in your blood, is leaking into your urine. A result below 30 milligrams per gram is considered normal. A result of 30 or higher may indicate early kidney damage. Doctors often repeat the test to confirm results.
Twenty-Four Hour Urine Test
This test measures everything your kidneys excrete over a full day. It can show total protein loss and levels of minerals linked to kidney stones or specific kidney diseases. It requires collecting all urine for twenty-four hours, but it provides information that spot tests cannot.
Nephrin Test
Nephrin is a protein found in podocytes, the kidney cells that help filter blood. When nephrin appears in urine, it may signal early injury to these cells. This test is not routine, but it is becoming more common in specialized evaluations.
Imaging Tests
Kidney Ultrasound
A painless test that uses sound waves to create images of the kidneys. It can show kidney size, shape, cysts, stones, blockages, and other structural changes. It usually takes twenty to thirty minutes.
CT Scan
A CT scan uses X rays and computer technology to create detailed images. It is helpful when doctors need more information than an ultrasound can provide. Some scans use contrast dye, which may require precautions for people with kidney disease. A CT scan usually takes thirty to sixty minutes.
MRI
An MRI uses magnets and radio waves to create three dimensional images. It is useful when ultrasound or CT results are unclear. Some MRI scans use contrast dye, and people with kidney disease may need a kidney function test before receiving it. An MRI usually takes thirty to sixty minutes.
Kidney Biopsy
A biopsy involves removing a very small piece of kidney tissue for examination under a microscope. It helps doctors understand the exact type of kidney disease, how severe it is, and which treatments may help.
Doctors may recommend a biopsy if you have blood or protein in your urine, kidney disease without a clear cause, nephrotic syndrome, suspected inflammatory disease, or a transplanted kidney that is not working well.
Genetic Testing
Genetic testing looks for inherited causes of kidney disease. It can be done with a blood or saliva sample and is helpful when kidney disease runs in the family or when the cause is unclear. Results can guide diagnosis, monitoring, and treatment. Many people choose to work with a genetic counselor to understand their results and next steps.
What to Know About Cost
The cost of kidney tests varies depending on insurance coverage. It is reasonable to ask your doctor and your insurance company which tests are covered and what your out of pocket costs may be. Many clinics have social workers or financial counselors who can help you explore assistance programs if needed.
What to Remember
Kidney tests help you and your care team understand what is happening inside your body. The most important step is to stay informed and ask questions. When you understand your results, you are better able to protect your kidney health for the long run.
Resources:
Tests for kidney disease – American Kidney Fund