The only way to know how well your kidneys are working is to get tested. Kidney disease often has no symptoms until your kidneys are badly damaged. Testing is especially important if you have diabetes, high blood pressure or a family history of kidney disease.
Ask your doctor about these kidney tests. Finding and treating kidney disease early can help you slow or stop damage to your kidneys.
Blood test: eGFR
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.
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)
Blood test: 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.
One way your doctor can look at your kidneys is by doing a kidney ultrasound. A kidney ultrasound (also called a renal ultrasound) is a safe and painless test that uses sound waves to make images of your kidneys.
Your doctor may use an ultrasound to look at your kidneys if they think there may be a problem with your kidneys. A kidney ultrasound can show:
- Something abnormal in the 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
- Your bladder (the organ that stores urine before it leaves your body)
Your doctor may also use a kidney ultrasound to:
- Help guide needles during a kidney biopsy (a procedure where your doctor takes a very small piece of your kidneys and looks at it under a microscope)
- Check on your transplanted kidney
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.