⚠️ Educational only. LabPlain does not provide medical advice or diagnosis. Always discuss your specific results with your healthcare provider.
What this test measures
eGFR stands for estimated Glomerular Filtration Rate. It measures how well your kidneys are filtering waste products out of your blood — specifically, how many milliliters of blood your kidneys clean per minute. It's one of the most important numbers for assessing kidney health.
Your kidneys contain about one million tiny filtering units called glomeruli. When they're working properly, they filter roughly 90–120 mL of blood every minute, removing waste while keeping things your body needs — like protein and blood cells — in your bloodstream. When kidney function declines, the eGFR number drops.
eGFR is calculated (not directly measured) using your creatinine level, age, and sex. It's routinely included in a Comprehensive Metabolic Panel (CMP) and is the primary tool doctors use to diagnose and track chronic kidney disease (CKD).
A single number above 60 is generally considered normal for adults. However, eGFR naturally declines with age — a 75-year-old with an eGFR of 65 may have perfectly healthy kidneys for their age. Context always matters.
eGFR is used to stage chronic kidney disease (CKD) from Stage 1 (mildly reduced, or normal with signs of damage) to Stage 5 (kidney failure). See the stages table below.
⚠️ One number isn't enough
A single low eGFR reading doesn't automatically mean you have kidney disease. Dehydration, intense exercise, certain medications, and even eating a large protein meal can temporarily lower eGFR. Doctors require two or more low readings taken at least 3 months apart before diagnosing CKD.
CKD stages by eGFR
Stage
eGFR
What It Means
G1
≥ 90
Normal or high — kidney damage may still be present if other markers are abnormal
G2
60–89
Mildly decreased — often no symptoms, monitoring recommended
G3a
45–59
Mild to moderately decreased — lifestyle changes and closer monitoring needed
G3b
30–44
Moderately to severely decreased — specialist referral often recommended
G4
15–29
Severely decreased — preparing for kidney replacement therapy
G5
< 15
Kidney failure — dialysis or transplant required
What your result might indicate
↓ If Low (below 60)
May indicate chronic kidney disease, acute kidney injury, diabetic nephropathy, hypertensive kidney damage, or severe dehydration. Follow-up testing is essential before any diagnosis.
↑ If Very High (>120)
Very high eGFR can occasionally occur in early diabetes or pregnancy due to hyperfiltration — the kidneys working harder than normal. This can actually be a sign of early stress on the kidneys.
Symptoms of reduced kidney function
One of the most dangerous things about kidney disease is that it often causes no symptoms until function is significantly reduced. When symptoms do appear, they may include:
↓ Low eGFR Symptoms
Swelling in legs, ankles, or feet
Fatigue and weakness
Decreased urine output
Foamy or dark urine
Shortness of breath
Nausea or loss of appetite
Difficulty concentrating
High blood pressure
Early Warning Signs
Waking up at night to urinate
Persistent puffiness around the eyes
Muscle cramps, especially at night
Dry, itchy skin
Changes in urine color or frequency
High blood pressure that's hard to control
Unexplained anemia
Metallic taste in the mouth
Common causes of low eGFR
Chronic causes
The two leading causes of chronic kidney disease worldwide are diabetes and high blood pressure. In diabetes, high blood sugar gradually damages the delicate filtering vessels in the kidneys (diabetic nephropathy). In hypertension, elevated pressure damages the blood vessels supplying the kidneys over time. Together, these two conditions account for roughly two-thirds of all CKD cases.
Other chronic causes include glomerulonephritis (inflammation of the kidney's filters), polycystic kidney disease (an inherited condition causing cysts to form in the kidneys), lupus and other autoimmune diseases, and long-term use of NSAIDs like ibuprofen or naproxen.
Acute causes
A sudden drop in eGFR — called acute kidney injury (AKI) — can result from severe dehydration, a major infection, certain medications (including contrast dye used in CT scans), a urinary blockage, or a sudden drop in blood pressure. AKI is often reversible if the underlying cause is treated quickly.
Tests often ordered alongside eGFR
eGFR is almost always interpreted alongside other markers of kidney function and overall metabolic health:
Creatinine — the waste product eGFR is calculated from; elevated creatinine is the direct signal
BUN (Blood Urea Nitrogen) — another waste product filtered by the kidneys; often reported alongside creatinine
Urine albumin-to-creatinine ratio (uACR) — detects protein leaking into urine, a key early sign of kidney damage even when eGFR is normal
Electrolytes (sodium, potassium, bicarbonate) — kidney disease disrupts the body's ability to balance these minerals
Complete blood count (CBC) — kidneys produce erythropoietin, which stimulates red blood cell production; CKD often causes anemia
Phosphorus and calcium — kidneys regulate these minerals; imbalances are common in advanced CKD
What to do next
A single low eGFR is not a diagnosis. Your doctor will want to repeat the test and check a urine protein test before drawing any conclusions. If you have diabetes or high blood pressure, regular eGFR monitoring is standard practice — catching a decline early is the best way to slow it down. Lifestyle changes (controlling blood pressure and blood sugar, staying hydrated, limiting NSAIDs, and eating a kidney-friendly diet) can meaningfully slow CKD progression.
Questions to ask your doctor
01Is this a one-time reading, or do I have a pattern of low eGFR over several tests?
02Should I have a urine protein test to check for albumin in my urine?
03Could my diabetes or blood pressure be contributing to this result?
04Are any of my medications — including over-the-counter pain relievers — affecting my kidneys?
05Do I need to see a nephrologist (kidney specialist)?
06What dietary changes would help protect my kidney function?
07How often should I be monitoring my eGFR going forward?
Frequently asked questions
Can eGFR improve if it's low?
It depends on the cause. If the low reading is due to something temporary — dehydration, a medication, or an acute illness — eGFR can return to normal once the cause is addressed. In chronic kidney disease, the goal is usually to slow further decline rather than fully reverse it. However, treating the underlying cause (like controlling blood pressure or blood sugar) can sometimes lead to meaningful improvement.
Does eGFR naturally decline with age?
Yes. eGFR typically decreases by about 1 mL/min/year after age 40, simply as a result of normal aging. This is why a result of 65 in a 75-year-old is interpreted very differently than the same result in a 35-year-old. Your doctor uses age-specific context to interpret your number.
Is eGFR the same as creatinine?
No, but they're closely related. Creatinine is a waste product your kidneys filter out of the blood. eGFR is a calculated estimate of kidney filtering capacity that uses your creatinine level as its main input, along with your age and sex. A high creatinine typically corresponds to a low eGFR — both point to reduced kidney function.
What foods should I avoid if my eGFR is low?
People with reduced kidney function are often advised to limit high-potassium foods (bananas, oranges, potatoes), high-phosphorus foods (dairy, nuts, dark colas), and sodium. Protein intake may also need to be moderated in later stages. A registered dietitian who specializes in kidney disease (a renal dietitian) can create a personalized plan — dietary needs vary significantly by CKD stage.
Can I still donate a kidney if I have a borderline eGFR?
Kidney donation eligibility depends on many factors including eGFR, overall health, age, blood pressure, and urine protein levels. A borderline eGFR would likely be a concern for donation, since donors need sufficient kidney reserve to remain healthy with one kidney. A transplant center's evaluation team would assess this in detail.