Estimated Glomerular Filtration Rate (eGFR)

What is estimated glomerular filtration rate (eGFR)?

Glomeruli are tiny filters in your kidneys that help remove toxins (waste) from your blood. Estimated glomerular filtration rate (eGFR) measures how much blood these filters clean every minute based on your body size. When you have a routine blood test, eGFR is often part of the basic metabolic panel.

What does eGFR tell healthcare providers?

eGFR helps healthcare providers spot problems with your kidneys, including kidney disease.

Your kidneys are part of the urinary system. Kidney disease occurs when one or both kidneys have damage. When you have kidney disease, the glomeruli filter less blood. As a result, dangerous toxins can build up in your blood.

Kidney disease symptoms, such as frequent urination and muscle spasms, may not occur until you lose up to 40% of kidney function. eGFR helps providers detect the disease early so that you can start treatments to slow or stop kidney damage.

Who might need to know their eGFR?

Healthcare providers use eGFR to watch for the onset of kidney disease. The test also shows the severity (stage) of existing kidney disease.

Certain health conditions increase your risk for kidney problems. Your provider may use eGFR to monitor kidney health if you have or take medications to treat:

• Birth defects that affect kidney function.
• Coronary artery disease or heart disease.
• Diabetes.
• Family history of kidney disease.
• Frequent urinary tract infections (UTIs) or urinary blockages.
• High blood pressure.
• History of smoking.
• Obesity.

How do healthcare providers determine eGFR?

Tests to precisely measure GFR are highly complex. For this reason, they typically only take place for research or transplant purposes. Instead, healthcare providers use a formula to come up with an estimated GFR (eGFR). The formula combines results from a serum creatinine blood test with information like your age and gender.

A serum creatinine blood test measures levels of creatinine, a waste product in your blood. Your body makes and uses creatine, a chemical, to provide energy to muscles. When muscles use this energy, muscle tissue breaks down, releasing creatinine (a toxin) into the blood. Healthy kidneys filter this toxin out of the blood and your body gets rid of it when you urinate. But when you have kidney disease, creatinine stays in the blood and gradually builds up.

To determine eGFR, your provider uses a National Kidney Foundation calculating system. This system factors in your:

• Creatinine level.
• Age.
• Sex.
• Height and weight.
• Race and/or ethnicity.

How should I prepare for a serum creatinine blood test?

The serum creatine blood test is highly sensitive. Follow your healthcare provider’s guidelines to prepare for the blood test. You may need to fast (drink only liquids and not eat solid foods) for a time before the test. You may also need to stop taking certain medications.

Your provider may also advise that you not eat cooked meat the day before the test. Some studies show that eating meat raises creatinine levels temporarily.

What do eGFR numbers mean?

Healthcare providers measure eGFR in milliliters of cleansed blood per minute per body surface (a measurement that reads mL/min/1.73m2).

Values for eGFR vary depending on age, sex and other factors. The rate naturally declines as you age and lose muscle mass. The average eGFR for someone in their 20s is about 116 mL/min/1.73m2. It drops to 85 mL/min/1.73m2 for people in their 60s.

An eGFR higher than 60 means you have at least 60% kidney function. Generally, the higher the number, the better your kidney function.

Why are there different eGFR numbers for Black and non-Black people?

Your test report may show two eGFR numbers, one for Black people and one for those who are not Black. People of African ancestry have a higher eGFR. They produce more creatinine and have more muscle mass than non-Black people. The lab doesn’t know your ethnicity or race, so the report includes both numbers.

How does the eGFR number relate to kidney disease?

Your provider may diagnose chronic kidney disease when your eGFR stays below 60 for three months in a row.

There are five stages:

• Stage 1 (eGFR of 90 or higher) indicates mild kidney damage, but your kidneys are working well.
• Stage 2 (eGFR between 60 and 89) indicates an increase in kidney damage from stage 1, but the kidneys continue to function well.
• Stage 3 (eGFR between 30 and 59) means you have decreased kidney function and may experience symptoms.
• Stage 4 (eGFR between 15 and 29) is poor kidney function, with moderate to severe kidney damage.
• Stage 5 (eGFR below 15) is a sign of kidney failure. It means you have less than 15% kidney function. This stage is the most serious and can be life-threatening. You will need dialysis (a machine to filter your blood) or a kidney transplant.

What follow-up tests take place after an abnormal eGFR?

To assess kidney damage or find the cause of an abnormal eGFR, your healthcare provider may order one or more of these tests:

• Urinalysis to look for albumin (a protein) and blood in urine, early signs of kidney disease.
• Kidney ultrasound or CT scan to check for kidney stones, kidney cancer or urinary tract problems.
• Creatine clearance test to measure creatinine levels in urine and blood at the same time.
• Kidney biopsy to determine the type and severity of kidney disease.

When should I call the doctor?

If you have kidney disease or disease risk factors, call your healthcare provider if you experience:

• Frequent urination, blood in urine or foamy urine.
• Dry, itchy skin or darkening of skin.
• Extreme fatigue.
• Muscle spasms and cramps.
• Nausea or vomiting.
• Shortness of breath.
• Swollen hands, feet or ankles.

A note from Cleveland Clinic

Monitoring your eGFR is important if you’re at risk for kidney disease or already have it, including if you take certain medications. If eGFR indicates some degree of kidney disease, you can take steps to protect your kidneys from further damage. Your healthcare provider can prescribe medications to manage high blood pressure or diabetes. You can also improve kidney health by losing weight (if needed), exercising and eating a nutritious, low-salt diet.