Glomerular Filtration Rate (GFR) Test
Reviewed
Also called: estimated GFR, eGFR, calculated glomerular filtration rate, cGFR
An eGFR and mGFR test are used to see if your kidneys are filtering waste at a healthy rate.
Specimen: Blood
Why this test may be ordered
- Screen for kidney disease in people without symptoms
- Help diagnose kidney disease in people who have symptoms
- Help find out how serious kidney disease is
- Monitor people with chronic kidney disease (CKD) to see if treatment is helping
- Check kidney health before people start certain treatments that could affect their kidneys
Preparation and collection
Your provider will let you know how to prepare for your eGFR test. You may need to fast (not eat or drink) or avoid certain foods, such as meat, for several hours before the test. This is because some foods like meat can affect your eGFR score. Certain medicines can also affect your results. So be sure to tell your provider everything you're taking. But don't stop taking any medicine unless your provider tells you to. If you're getting an mGFR test, you may need to fast or avoid certain foods before the test.
For eGFR testing, a health care professional will take a blood sample from a vein in your arm, using a small needle. This usually takes less than five minutes. For mGFR testing, a health care professional will inject you with a substance called a filtration marker. To see how well your kidneys do this, a health care professional will take a blood sample every 2 to 3 hours. They may also take a sample of your urine (pee).
There is very little risk to having a blood test for an eGFR test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly. In some cases, the substances used during an mGFR test can cause an allergic reaction. However, this isn't common.
Understanding results
Your eGFR results may be reported as a number that shows how much blood your kidneys filter per minute. Because eGFR can vary from person to person based on factors like age, body size, and other health conditions, your provider can help you understand how these general ranges apply to you.
- eGFR between 90 and 100: An eGFR between 90 and 100 means that you probably don't have kidney disease. Limitation: An eGFR isn't a perfect test and may not always reflect kidney damage. Next step: Ask your provider to explain what your eGFR says about your kidney health.
- eGFR between 60 and 90: An eGFR between 60 and 90 means you may have early-stage kidney disease. Limitation: It's also possible to have an abnormal result even if you don't have kidney damage. Next step: If your eGFR is lower than what's normal for you, your provider may order other tests that check your kidney health.
What does a low eGFR mean?
eGFR between 15 and 60: An eGFR between 15 and 60 means that you may have kidney disease. Limitation: An eGFR isn't a perfect test and may not always reflect kidney damage. Next step: If your eGFR is lower than what's normal for you, your provider may order other tests that check your kidney health.- eGFR below 15: An eGFR below 15 means that you may have kidney failure. Limitation: Because eGFR can vary from person to person based on factors like age, body size, and other health conditions, your provider can help you understand how these general ranges apply to you. Next step: If you're diagnosed with kidney disease, your provider will explain what you can do to protect your kidneys from more damage and help prevent kidney failure.
- eGFR is an estimate and may not always reflect kidney damage.
- It's possible to have an abnormal result even if you don't have kidney damage.
- eGFR isn't a perfect test and may not always reflect kidney damage.
What to do next
If you're diagnosed with kidney disease, your provider will explain what you can do to protect your kidneys from more damage and help prevent kidney failure.
- What does my eGFR number mean for my kidney health?
- Do I need to fast or avoid any foods before the test?
- What medicines might affect my eGFR results?
- How often should I have this test if I have diabetes or high blood pressure?
- What other tests might I need to check my kidney function?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: Glomerular Filtration Rate (GFR) Test