Estimated Glomerular Filtration Rate Test

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KEY POINTS

• The estimated glomerular filtration rate (eGFR) test helps measure how well the kidneys are working.
• An eGFR number lower than normal usually means that one or both kidneys are not working well because of disease or a problem in your urinary system.
• Talk to your healthcare provider about your result and ask any questions you may have.

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What is the estimated glomerular filtration rate test?

The estimated glomerular filtration rate (eGFR) test helps measure how well the kidneys are working. The eGFR is a number that the lab reports along with the number from another blood test called a creatinine test.

Glomeruli are tiny filters in the kidneys that help remove waste products from the blood. The amount of blood that is filtered by the glomeruli per minute is called the glomerular filtration rate (GFR). The GFR decreases and waste products build up in the blood when your kidneys do not work well.

Muscles make creatinine when another chemical, creatine, is broken down to produce energy for the muscles. This waste product is carried by the blood to the kidneys, which filter it from the body into the urine.

The eGFR is also called a calculated estimated glomerular filtration rate (cGFR).

Why is this test done?

This test is done to see how well your kidneys are working. It can help diagnose kidney disease and monitor treatment for kidney disease. You may have this test if you have:

• Diabetes
• High blood pressure
• A family history of kidney disease
• Frequent urinary tract infections
• Heart disease

How do I prepare for this test?

• You may need to avoid taking certain medicines before the test because they might affect the test result. Make sure your healthcare provider knows about any medicines, herbs, or supplements that you are taking. Ask your provider before stopping any of your regular medicines.
• Tell your healthcare provider if you are pregnant or if you may be pregnant.
• Talk to your healthcare provider if you have any questions about the test.

How is this test done?

Blood Test

A small amount of blood is taken from a vein in your arm with a needle. The blood is collected in tubes and sent to a lab to measure the creatinine level. Then the lab uses your creatinine level to do a calculation to see how well the tiny filters in the kidney are working.

The lab will use information about you to be able to calculate your eGFR test result:

• Height
• Weight
• Gender
• Age
• Ethnic background

Ask your healthcare provider when and how you will get the results of your test.

What does the test result mean?

An eGFR number lower than normal usually means that one or both kidneys are not working well because of disease or a problem in your urinary system.

• Some medicines can affect the test results.
• Pregnancy can affect the test results.
• Older age can lower your eGFR.

What if my test result is not normal?

Test results are only one part of a larger picture that takes into account your medical history and current health. Sometimes a test needs to be repeated to check the first result. Talk to your healthcare provider about your result and ask questions, such as:

• If you need more tests
• What kind of treatment you may need
• What lifestyle, diet, or other changes you might need to make