Glomerular Filtration Rate
Does this test have other names?
GFR, estimated glomerular filtration rate, EGFR
What is this test?
This is either a blood test or a urine test that looks for changes in how your kidneys
function. Your kidneys have tiny filters called glomeruli. The filters help remove
waste from your blood. Your glomerular filtration rate is the rate at which your blood
is filtered each minute. A glomerular filtration rate can be estimated with great
accuracy, based on your weight and age. This is called the estimated glomerular filtration
rate, or EGFR.
Why do I need this test?
You might have this test to see if your kidneys are working the way they should, especially
if you have diabetes or high blood pressure. GFR can detect kidney disease in its
earliest stages, when it is most treatable. GFR can also help figure out if you have
a condition that causes decreased blood flow to the kidneys, such as congestive heart
failure, shock, or severe fluid loss (dehydration).
What other tests might I have along with this test?
Your healthcare provider is likely to order other tests that measure kidney function
and waste products, such as:
What do my test results means?
A lab test result may be affected by many things, including the method the laboratory
uses to do the test. If your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
The normal range for GFR depends on your age, weight, and muscle mass. Here are typical
A GFR above 60 is considered normal.
A GFR below 60 may mean you have kidney disease.
A GFR of 15 or below means your kidneys could be failing.
If your test results indicate you have early kidney disease, your healthcare provider
may want to take steps to treat it aggressively.
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
arm. You may also need to collect a 24-hour urine sample.
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly sore. A urine test
poses no known risks.
What might affect my test results?
Your test results may be affected if you:
Exercised vigorously before testing
Are severely malnourished, are underweight, or have muscle-wasting disease
Are severely overweight
Are a bodybuilder
Have a neuromuscular disorder
Are taking certain medicines, including chemotherapies and kidney medicines
Eat a lot of meat
Eat a vegetarian or low-meat diet
Take creatine supplements
Have other serious health conditions
An incomplete urine specimen also can give false results.
How do I get ready for this test?
No special diet is required. Check with your healthcare provider about taking any
medicines on testing day. And be sure your healthcare provider knows about all medicines,
herbs, vitamins, and supplements you are taking. This includes medicines that don't
need a prescription and any illicit drugs you may use.
If you need to collect a 24-hour urine sample, be sure you understand how to do it.