Urological Health Chronic Kidney Disease Estimated Glomerular Filtration Rate (eGFR) Test Here's what to expect when undergoing this test By Tolu Ajiboye linkedin Tolu Ajiboye is a health writer who works with medical, wellness, biotech, and other healthcare technology companies. Learn about our editorial process Tolu Ajiboye Medically reviewed by Medically reviewed by Matthew Wosnitzer, MD on June 24, 2020 twitter linkedin Matthew Wosnitzer, MD, is board-certified in urology. He is an attending physician at Yale New Haven Health System, Northeast Medical Group and teaches at the Frank Netter School of Medicine. Learn about our Medical Review Board Matthew Wosnitzer, MD on June 24, 2020 Print Table of Contents View All Table of Contents Purpose of Test Risks Before the Test During the Test After the Test Interpreting Results Follow Up An estimated glomerular filtration rate (eGFR) test is a blood test that’s used to figure out how well your kidneys are doing their job. The test measures the amount of creatinine in your blood and, using a formula, mathematically derives a number that estimates how well your kidneys are functioning. The formula uses your creatinine levels, age, sex, weight, and race to arrive at that number—your eGFR. Yoshiyoshi Hirokawa / Getty Images Purpose of Test Your doctor will order an eGFR test if he suspects you have chronic kidney disease. So, if you complain about having symptoms of kidney disease, your doctor may order you to take an eGFR test. These symptoms include: Dry and persistently itchy skinMuscle crampsSwollen ankles and feetIncrease in frequency of urinationFoamy or bloody urineSleep problemsFatigue and low energy levelsConcentration problemsNausea and vomitingPoor appetiteHigh blood pressure Early-stage kidney disease doesn't normally have any symptoms. Because of this, if you have any preexisting conditions like diabetes, high blood pressure, and cardiovascular disease—all of which tend to affect your kidneys—your doctor will likely order this test for you at regular intervals. A family history of kidney disease could also necessitate this test. Further, if you’ve already been diagnosed with kidney disease, your doctor will likely still order an eGFR test regularly to monitor how well your kidneys are faring. The main function of your kidneys is to clean your blood. The glomeruli, tiny filters found in your kidneys, are central to this job. So, your eGFR rate is actually how much blood these glomeruli filter per minute, and it works by measuring the levels of creatinine in your blood. Creatinine is one of the types of waste that the kidneys help to filter out of the body. Therefore, if a high level of creatinine is found in your blood, it might signal that your kidneys (the glomeruli, in particular) aren't doing a good job of filtering and cleaning out your blood. Limitations The eGFR test is not 100 percent accurate and it can only give an estimate of your filtration rate. Additionally, the standard formula for calculating eGFR is not valid for people under the age of 18. An eGFR test is usually ordered alongside a urine test for albumin to diagnose kidney disease. In the same vein, just as eGFR tests are used to monitor kidney disease, urine tests for albumin are generally used concurrently for the same purpose. Albumin is a protein that’s normally found in your blood, and properly functioning kidneys do not allow it to get into your urine. However, damaged ones do. So if the results of this test show that there's albumin in your urine, there’s a high chance you have kidney disease. Albumin in the urine is called albuminuria. A urinalysis may also be ordered to enable the doctor to check for any signs of kidney damage in your urine. More Kidney Function Tests and What They Mean Risks There are generally no risks or contraindications associated with eGFR testing. Before the Test You can expect to discuss your symptoms with your doctor, as well as your family history of kidney disease (if any). You should disclose all medications you are taking to your doctor. This is because certain drugs can interfere with eGFR results because they increase your creatinine levels. Some of these drugs are cisplatin and gentamicin. You should expect to discuss your medical history and if you have conditions like diabetes and high blood pressure, you should disclose that too. Disclose if you are pregnant or if there's any chance you may be, as this can affect the test results. Timing Because the test takes the form of a blood test, it will just take a few minutes. Location The test will take place in the hospital. What to Wear You can dress however you want for this test. However, keeping in mind that the blood will be drawn from your arm, it may be better for you to wear sleeveless clothes or clothes with which uncovering your arm will be easy. Food and Drink Your doctor may or may not instruct you to not eat anything on the day of the test or to avoid certain foods. He may also instruct you to stop taking certain medications. During the Test A needle will be inserted into the skin on your arm and your blood will be drawn. You may feel a moderate amount of pain or merely a sting, and the entire process will probably take under a minute to complete. After the Test You will be allowed to go home immediately, and your doctor (or the technician who attended to you) will tell you when to return for your test results. You will be instructed to report back to the hospital if you notice any bleeding or serious bruising at the site where the needle was inserted. Side Effects There are some very common side effects of undergoing a blood test like eGFR. You shouldn’t worry if you experience any of these side effects and can expect them to go away very soon:Slight bruising or swellingSlight stinging or throbbingFeeling lightheaded or dizzyHowever, serious and rare side effects of having your blood drawn are:Excessive bleedingInfectionA swollen area filled with blood. This is also called a hematoma.You should report back to your doctor immediately if you any experience any of these. Interpreting Results Your eGFR result will be a number and this is what each range of numbers means: GFR 90 and above: You have normal to high kidney function.GFR 60–89: There is a mild reduction of kidney function. This does not mean you have kidney disease. It is only when there are other signs of kidney damage that this GFR number may signify kidney disease.GFR 45–59: There is mild to moderate reduction in kidney function, and it may signify that you have kidney disease.GFR 30–44: This shows that there is a moderate to severe reduction of kidney function.GFR 15–29: This signifies a severe reduction of kidney function.GFR 15 or less: This signifies kidney failure and you will need to be on dialysis or get a kidney transplant. This being said, it is only your doctor that can give you the most accurate interpretation of your results based on your eGFR result and other individual symptoms, complications, and medical history. You should also note that your eGFR test result can be influenced by many factors. This means that you may not get a correct eGFR result if: You’re pregnantYou’re under the age of 18You’re elderly, as you’re likely to have a low eGFR if you’re elderly because GFR normally declines with ageYou’re on a vegan or vegetarian dietYou’re significantly more or less muscular than the average person Accordingly, your doctor will look at these things, if any apply to you, before making a diagnosis of chronic kidney disease (CKD), or ordering further tests to confirm the diagnosis. How Chronic Kidney Disease Is Diagnosed Follow Up Depending on your eGFR test result and other surrounding medical information, your doctor may not make a definitive diagnosis of kidney disease. Instead, he/she may ask you to come back for another eGFR test to check if the result remains the same. If you’ve been diagnosed with kidney disease from your eGFR test results, your doctor may order the following tests for you: Kidney biopsy: This test involves taking a small price of your kidney for microscopic examination. This is done in order to determine the exact type of kidney disease you have, and how far the disease has progressed so that an appropriate treatment plan can be devised.Ultrasound or CT Scan: Either of these imaging tests may be ordered so that your doctor can get a clear picture of your kidneys, and determine what state they’re in. In addition to this, your doctor may also refer you to a nephrologist—a doctor that specializes in kidney problems—to determine the next steps and help manage your condition. It is extremely necessary to have an open and detailed conversation about your eGFR result with your doctor. If you’d like, you can also opt to take the test in another hospital or seek out a second medical opinion on your initial diagnosis. A Word From Verywell It is impossible to reduce your eGFR, you can only keep it from reducing. So, regardless of what your eGFR test results are, it’s important to make healthy lifestyle choices. Eating healthy, quitting smoking and being physically active are some of the things you can do to make sure this doesn’t happen. If you’re particularly at risk of developing kidney disease, you should set up a regular schedule to get your GFR checked. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. The Renal Association. About eGFR. NIH. Medline Plus. Glomerular filtration rate (GFR) test. Updated March 24, 2020. National Kidney Foundation. GFR. NIH National Institute of Diabetes and Digestive and Kidney Diseases. Chronic kidney disease tests & diagnosis. Updated October 2016. UCSF Health. Glomerular filtration rate. National Kidney Foundation. Estimated glomerular filtration rate (eGFR). Updated 2018. University of Rochester Medical Center. Glomerular filtration rate. National Kidney Foundation. GFR (Glomerular filtration rate) A key to understanding how well your kidneys are working. Updated 2013. Harvard Health Publishing. Weak kidneys? Pay attention but don't worry excessively. Updated May 2013. Additional Reading About eGFR. The Renal Association. Chronic Kidney Disease Tests & Diagnosis. NIDDK - National Institute of Diabetes and Digestive and Kidney Diseases. Glomerular Filtration Rate. UCSF Medical Center. Estimated Glomerular Filtration Rate (eGFR). Labtestsonline.org.