Glomeruler Filtration Rate (eGFR)
Overview
Estimated Glomerular Filtration Rate
Your kidneys filter your blood by removing waste and extra water to make urine. The glomerular filtration rate (GFR) shows how well the kidneys are filtering. An estimated 37 million adults in the United States may have chronic kidney disease (CKD) and can take the steps needed to protect their kidney function when it is found early.
Types
Measuring and estimating GFR
Getting an accurate GFR level is challenging because measured GFR (mGFR) is a complicated and lengthy process, which is impractical for both clinicians and patients. It is for this reason that healthcare professionals use a formula to estimate GFR (eGFR). Reliable estimates of GFR are important for identifying kidney disease, which often has no symptoms until just before the kidneys fail. The standard way to estimate GFR is with a simple blood test that measures your creatinine levels. Creatinine is a waste product that comes from the digestion of dietary protein and the normal breakdown of muscle tissue. Aside from CKD, creatinine levels can be affected by other factors including diet; muscle mass, which is the weight of your muscles; malnutrition; and other chronic illnesses.
Differences between eGFR and mGFR
| Estimated GFR (eGFR) | Measured GFR (mGFR) | |
| How it works | A calculation used to estimate how well your kidneys are filtering certain agents produced by your body, such as: creatinine (a waste product that comes from the normal wear and tear on muscles) cystatin C (a protein that slows down the breakdown of other protein cells) | A measurement of how well your kidneys are filtering certain agents not produced by your body, such as: inulin (a kind of fiber that is found in some plant foods) iohexol (contrast agent used in imaging tests) |
| Availability | Widely available | Not widely available |
| Cost | Not expensive | Expensive |
| Accuracy | Possible inaccurate estimates of GFR, especially in early stages of kidney disease (stages 1 and 2)* | Accurate measures of GFR, including early stages of kidney disease (stages 1 and 2) |
| Precision | Can miss early GFR changes, such as a rapid decrease in levels, which may be a sign of diabetic kidney disease | Can identify early GFR changes, such as a rapid decrease in levels, which may be a sign of diabetic kidney disease |
Purpose
Why eGFR testing is done
Early stage kidney disease doesn’t usually cause symptoms, but your doctor may recommend a eGFR test if you are at higher risk of developing kidney disease. CKD risk factors include:
- Having diabetes or high blood pressure
- High blood pressure
- Being overweight
- Family history of kidney failure
Later stage CKD does cause symptoms. So you may need an eGFR test if you have any of the following symptoms:
- Urinating more or less often than usual
- Itching
- Feeling tired
- Swelling in your arms, legs, or feet
- Muscle cramps
- Nausea and vomiting
- Loss of appetite
Kidney Numbers and CKD Heat Map
Watch a series of short, animated videos that will help you learn about the importance of knowing your kidney numbers, how the heat map works for identifying where you are in terms of kidney health and along with some tips for improving your kidney numbers and moving in the right direction on the heat map.
Risks
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Preparation
You may need to fast (not eat or drink) or avoid certain foods for several hours before the test. Your health care provider will let you know if there are any special instructions to follow.
Process
What to expect
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
After the test
There are typically no restrictions after blood is drawn for the test.
Results
eGFR of 90 or higher is in the normal range
eGFR of 60 -89 may mean early kidney disease
eGFR of 15 -59 may mean kidney disease
eGFR below 15 may mean kidney failure
What is a normal eGFR number?
In adults, the normal eGFR number is more than 90. eGFR declines with age, even in people without kidney disease. See chart below for average estimated eGFR based on age.
eGFR gets lower as we age (even when you don’t have kidney disease):
| Age (years) | Average eGFR |
| 20–29 | 116 |
| 30–39 | 107 |
| 40–49 | 99 |
| 50–59 | 93 |
| 60–69 | 85 |
| 70+ | 75 |
Understanding your results
There are five stages of kidney disease. Your healthcare provider determines your stage of kidney disease based on the amount of kidney damage shown by your eGFR or mGFR. Now that your know your eGFR, find out your kidney disease stage in the Kidney disease stage and eGFR table.
What are the stages of chronic kidney disease (CKD)?
| Stage | Description | eGFR | Kidney Function |
| 1 | Possible kidney damage (e.g., protein in the urine) with normal kidney function | 90 or above |
90-100% |
| 2 | Kidney damage with mild loss of kidney function | 60-89 |
60-89% |
| 3a | Mild to moderate loss of kidney function | 45-59 |
45-59% |
| 3b | Moderate to severe loss of kidney function | 30-44 |
30-44% |
| 4 | Severe loss of kidney function | 15-29 |
15-29% |
| 5 | Kidney failure | Less than 15 |
Less than 15% |
What to do next
Now that you know your eGFR and your stage of kidney disease, use this table to find questions to ask your healthcare professional at your appointments.
Kidney disease risk factors
Diabetes
High blood pressure
- Overweight/obesity
- Over the age of 60
- Family history of kidney disease or kidney failure
Usually, developing kidney disease is not due to any single reason, but because of a combination of physical, environmental, and social factors.
Questions for your healthcare team
| If your kidney disease is in stage… | Ask your healthcare professional if you should… | |||||
| 1 | 2 | 3a | 3b | 4 | 5 | |
 | | | | | | Test your urine because you have risk factors for kidney disease |
| | | | | | Repeat your eGFR test in 3 months to check that your eGFR remains lower than 90 | |
| | | | Take medication that may help slow progression of kidney disease (such as ACEs, ARBs, or SGLT2 inhibitors) | |||
| | | Adjust any current medications due to reduced kidney function | ||||
| | | | | Get nutritional and dietary counseling to help support kidney function and overall health | ||
| | | Start seeing a kidney specialist (nephrologist) | ||||
| | | Learn more about end-stage kidney disease and treatment options | ||||
| | Be evaluated for a kidney transplant and be placed on a kidney transplant list | |||||
Downloadable PDF
Download the eGFR Patient Flyer to keep this information on hand.
Kidney Numbers and the CKD Heat Map
Click here to download a printable resource that describes the kidney numbers that everyone should know and how your doctor uses them to diagnose chronic kidney disease (CKD). You will also learn how the kidney numbers fit onto the CKD Heat Map, which helps to guide your treatment plan.