What Is a Glomerular Filtration Rate (GFR)?

Medically Reviewed by Minesh Khatri, MD on January 27, 2022
2 min read

The glomerular filtration rate, or GFR, is a measure of how well your kidneys are cleaning your blood, which can be determined using an estimated GFR test (eGFR). 

The test gets its name from the parts of your kidney that filter waste out -- they’re called glomeruli.

Your doctor may do an eGFR test as part of a regular physical exam, or they might recommend it if you have signs of kidney problems. Those can include:

  • Problems peeing, including pain
  • Having to go more often or making less pee
  • Blood, foam, or a brownish color in your pee
  • Swelling or puffiness around your eyes, belly, wrists, or ankles
  • Pain in the middle of your back, near your kidneys

Your doctor probably will also want to check your eGFR if you have a condition that affects your kidneys, like certain autoimmune disorders, diabetes, high blood pressure, or heart disease. You may also get an eGFR test if other people in your family have had kidney disease.

Before your test, be sure to tell your doctor about any drugs, vitamins, or dietary supplements you take. They may tell you not to take certain medicines or eat certain foods beforehand.

For the test, a doctor or nurse will take a sample of your blood. Then they’ll send it to a lab to see how much creatinine is in it. To figure out your results, they’ll use a mathematical formula that’s based on the amount they find, along with your age and gender. Older formulas also used race as a factor, but they are being phased out.


In general, an eGFR result below 60 mL/min/1.73 m² can be a sign of kidney disease. But your doctor will be able to give you more specific information about your result, taking all your health information into account.

Your result might not be as accurate if you:

  • Are under 18
  • Are elderly
  • Are pregnant
  • Have a kidney condition or other serious illnesses
  • Have more muscle than average, like a bodybuilder
  • Have a disease that lowers your muscle mass
  • Follow a vegetarian diet
  • Are obese

If you’re in one of those groups, talk with your doctor about how your results might be affected.

Show Sources


National Kidney Foundation: “Glomerular Filtration Rate.”

National Institute of Diabetes and Digestive and Kidney Diseases: “Glomerular Filtration Rate.”

University of Rochester College of Medicine: “Glomerular Filtration Rate.”

University of North Carolina Kidney Center: “Glomerular Disease.”

American Journal of Roentgenology: “Kidney dimensions at sonography.”

Lab Tests Online: “Estimated Glomerular Filtration Rate,” “Creatinine.”

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