Estimated Glomerular Filtration Rate (eGFR)

Table of Contents

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.

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

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

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)

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 Estimated Glomerular Filtration Rate 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