Kidney Function & eGFR
Understanding Your Kidney Function
Your kidneys continuously filter your blood, removing waste products and excess fluid while helping maintain fluid, electrolyte, and blood pressure balance.
One of the most commonly used measures of kidney function is the estimated glomerular filtration rate, or eGFR. It is calculated using information from a blood test, including creatinine, and provides an estimate of how well your kidneys are filtering your blood.
eGFR is an estimate, not a perfect measurement. Your doctor looks at your eGFR together with urine tests, other laboratory results, your medical history, medications, and changes over time to understand your kidney health.
WhatDoes eGFR Mean?
In general, a higher eGFR indicates better kidney filtration. As kidney function decreases, eGFR usually decreases.
eGFR and Kidney Function
eGFR General interpretation
90 or higher Normal or high
60–89 Mildly decreased
45–59 Mild to moderate decrease
30–44 Moderate to severe decrease
15–29 Severe decrease
Below 15 Kidney failure range
These ranges are used when classifying kidney function in people with chronic kidney disease.
An eGFR of 60–89 does not automatically mean that you have chronic kidney disease. Evidence of kidney damage, such as albumin in the urine, may also be present when diagnosing CKD.
The Stages of Chronic Kidney Disease
Chronic kidney disease (CKD) is generally classified into stages based on kidney function and evidence of kidney damage.
Stage G1: eGFR 90 or higher, with evidence of kidney damage
Stage G2: eGFR 60–89, with evidence of kidney damage
Stage G3a: eGFR 45–59
Stage G3b: eGFR 30–44
Stage G4: eGFR 15–29
Stage G5: eGFR below 15, also called kidney failure
For CKD, the abnormality generally needs to be present for at least three months. A single abnormal eGFR does not necessarily mean that you have chronic kidney disease. Your doctor may repeat blood and urine testing to determine whether the change is persistent.
Why Can eGFR Change?
Your eGFR can change over time. A change in eGFR does not always mean that chronic kidney disease is getting worse.
Factors that can affect creatinine and eGFR include:
Age
Muscle mass
Diet
Certain medications
Acute illness or dehydration
Changes in kidney function
Because eGFR is an estimate, the trend in your kidney function over time is often more useful than looking at a single eGFR value.
How Does Creatinine Relate to eGFR?
Creatinine is a waste product produced by normal muscle activity. Healthy kidneys remove creatinine from the blood.
Your blood creatinine level is one of the important factors used to estimate eGFR. In general, as kidney filtration decreases, blood creatinine tends to increase and eGFR tends to decrease.
However, creatinine can also be affected by factors such as muscle mass, diet, and certain medications. For this reason, your doctor interprets creatinine and eGFR together with your overall health and other laboratory results.
In some situations, your healthcare provider may consider cystatin C, another blood marker that can be used to estimate kidney function. Using creatinine and cystatin C together can provide a more accurate estimate in certain situations.
eGFR Is Only Part of the Kidney Health Picture
Your eGFR tells us about how well your kidneys are filtering. It does not tell the entire story.
Another important kidney test is the urine albumin-to-creatinine ratio (uACR).
Albumin is a protein normally found in the bloodstream. Healthy kidneys generally keep albumin in the blood. When the kidney filters are damaged, albumin can leak into the urine.
What Does Your uACR Mean?
uACR General Interpretation
Less than 30 mg/g: normal to mildly increased
30–300 mg/g: moderately increased
More than 300 mg/g: severely increased
The combination of eGFR and urine albumin provides a more complete picture of kidney health and can help your healthcare provider assess the risk of kidney disease progression. Learn more about urine protein and albumin.
Does a Low eGFR Always Mean Kidney Disease?
Not necessarily.
One low eGFR result does not automatically mean that you have chronic kidney disease. An isolated decrease may occur during an acute illness, dehydration, or because of other factors that affect creatinine.
Chronic kidney disease is generally diagnosed when reduced kidney function or another marker of kidney damage persists for three months or longer.
Your physician may:
Review previous laboratory results
Repeat blood and urine testing
Review your medications
Check for protein or albumin in the urine
Evaluate blood pressure and other health conditions
Look for an underlying cause
This is why one laboratory value should be interpreted in context rather than viewed by itself.
Can Kidney Function Improve?
It depends on the cause.
Some temporary causes of reduced kidney function can be treated, and kidney function may improve.
With chronic kidney disease, the goal is often to protect the kidney function you have and slow further decline.
Managing conditions such as high blood pressure and diabetes, avoiding unnecessary medications that can harm the kidneys, maintaining a healthy lifestyle, and following an individualized treatment plan can help protect kidney health.
Your nephrologist can help determine the cause of reduced kidney function and develop a treatment and monitoring plan based on your individual risk factors and laboratory results.
When Should You See a Nephrologist?
A nephrology evaluation may be appropriate when there is:
Persistently reduced eGFR
Protein or albumin in the urine
Blood in the urine without an obvious cause
A significant or unexplained change in kidney function
Difficult-to-control high blood pressure
Recurrent kidney stones
Electrolyte abnormalities
Unexplained elevation in creatinine
Abnormal kidney imaging
A family history of kidney disease
Other concerns about kidney function
Early evaluation can be helpful because kidney disease may progress without noticeable symptoms in its earlier stages.
Frequently Asked Questions About eGFR
What is a normal eGFR?
An eGFR of 90 or higher is generally considered normal or high. However, eGFR should always be interpreted in the context of your age, overall health, urine findings, and other laboratory results.
Is an eGFR below 60 always kidney disease?
A persistently reduced eGFR below 60 may indicate chronic kidney disease. Your doctor will consider whether the reduction has persisted for at least three months and will also look for other evidence of kidney damage.
Can dehydration lower my eGFR?
Yes. Dehydration and acute illness can affect creatinine and may temporarily lower the estimated GFR. Your doctor may repeat testing after the underlying issue has been addressed.
Can eGFR improve?
Sometimes. If the decrease is related to a temporary or treatable condition, kidney function may improve. In chronic kidney disease, treatment focuses on protecting remaining kidney function and slowing further decline.
What does an eGFR of 50 mean?
An eGFR of 50 falls in the G3a range. However, the meaning of that number depends on whether it is persistent, your previous kidney function, urine albumin levels, and your overall medical history.
What is the difference between creatinine and eGFR?
Creatinine is a waste product measured in the blood. eGFR is an estimate of kidney filtration that uses creatinine and other information. Your healthcare provider considers both when evaluating kidney function.
Your Kidney Numbers Tell a Story
Rather than focusing on one laboratory value, kidney health is best understood by looking at the whole picture:
eGFR + urine albumin + blood pressure + medical history + medications + changes over time
If you have questions about your kidney function or an abnormal eGFR, a nephrologist can help determine what your numbers mean and whether further evaluation is needed.
Learn More
This information is intended for general educational purposes and does not replace medical advice. Your kidney function and laboratory results should be interpreted by your healthcare professional in the context of your individual health.