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Estimated Glomerular Filtration Rate (eGFR)

Overview

Estimated Glomerular Filtration Rate

Your kidneys filter your blood by removing waste and extra water to make urine. The kidney's filtration rate, called 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

GFR and eGFR

Testing for GFR can be a complicated and lengthy procedure, which is why doctors use a formula to estimate GFR or eGFR. Accurate estimates of the 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 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, malnutrition, and other chronic illnesses.

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

What are the Stages of Chronic Kidney Disease (CKD)?

Stage Description (GFR) At increased risk Risk factors for kidney disease (e.g., diabetes, high blood pressure, family history, older age, ethnic group) More than 90 Stage 1 Kidney damage with normal kidney function 90 or above Stage 2 Kidney damage with mild loss of kidney function 89 to 60 Stage 3a Mild to moderate loss of kidney function 59 to 44 Stage 3b Moderate to severe loss of kidney function 44 to 30 Stage 4 Severe loss of kidney function 29 to 15 Stage 5 Kidney failure Less than 15 Your GFR number tells you how much kidney function you have. As kidney disease gets worse, the GFR number goes down.

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

A GFR of 60 or higher is in the normal range.
A GFR below 60 may mean kidney disease.
A GFR of 15 or lower 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.

Age (years) Average eGFR
20–29 116
30–39 107
40–49 99
50–59 93
60–69 85
70+ 75
Date Reviewed: 09-23-2021