GFR stands for glomerular filtration rate: how much blood your kidneys filter each minute. Most US labs do not measure it directly. They estimate it — eGFR — from a blood creatinine level plus your age and sex, and sometimes your height and weight (MedlinePlus, National Library of Medicine, undated). MedlinePlus describes GFR as one of the most common blood tests used to check for chronic kidney disease.
One eGFR figure on one day is a snapshot, not a diagnosis. What it means depends on your other results, your symptoms, and whether the number has held steady over time.
What This Test Measures
eGFR is reported in millilitres per minute per 1.73 square metres of body surface area, written mL/min/1.73 m². Higher numbers mean faster filtering.
Result Range
What It May Indicate
Typical Next Step
90–120 mL/min/1.73 m²
The National Kidney Foundation describes this band as normal filtering. If urine tests show kidney damage, such as protein in the urine, the NKF calls this stage 1 CKD — possible damage with normal function.
Doctors often pair the eGFR with a urine albumin-creatinine ratio (uACR) before deciding anything.
60–89 mL/min/1.73 m² — borderline / indeterminate
Not enough on its own to say much. The NKF's stage G2 (kidney damage with mild loss of function) requires both an eGFR in this band AND evidence of damage, such as a uACR of 30 or higher, persisting for 3 months or more.
Typically a repeat eGFR plus a urine test; KDIGO (2024) notes chronicity is established by reviewing past GFR measurements.
45–59 mL/min/1.73 m²
The NKF describes this as stage 3a: mild to moderate loss of kidney function.
Repeat testing, urine testing, and a review of medicines and other conditions by your doctor.
30–44 mL/min/1.73 m²
The NKF describes this as stage 3b: moderate to severe loss of kidney function.
Closer monitoring; referral to a kidney specialist (nephrologist) is common.
15–29 mL/min/1.73 m²
The NKF describes this as stage 4: severe loss of kidney function.
Specialist care and planning discussions led by your clinical team.
0–15 mL/min/1.73 m²
The National Kidney Foundation's GFR graphic labels this band kidney failure.
Urgent specialist assessment.
A note on the ranges: these bands come from the National Kidney Foundation's staging descriptions, but the number your lab prints depends on which estimating equation it runs, and the equation already factors in age and sex (MedlinePlus, undated). NIDDK supports the NKF-ASN Task Force recommendation to use equations that do not include a race coefficient. Compare your result against your own earlier results, with your doctor, rather than against a band alone.
Get medical help the same day — emergency care if severe — if you pass little or no urine for a day, develop sudden swelling with shortness of breath, or become confused or drowsy alongside a kidney result.
What Can Affect Your Result
Creatinine is a waste product from muscle, so anything that changes how much of it is in your blood shifts the estimate, with or without kidney disease.
Muscle mass. Creatinine levels are influenced by muscle mass as well as age, sex and diet, which can affect the accuracy of estimated GFR (PubMed Central, National Center for Biotechnology Information, undated). MedlinePlus notes a creatinine clearance calculation may still help in people with very high muscle mass, or muscle loss from age, illness or limb loss.
A large cooked-meat meal or creatine supplements before the draw can raise blood creatinine temporarily.
Dehydration or acute illness on the day of the test can lower an eGFR that later returns toward your usual level.
Certain medicines. Serum creatinine is affected by medications that alter how the kidney excretes it, raising or lowering levels (PubMed Central, undated). Trimethoprim-sulfamethoxazole (Bactrim) is one example that can raise measured creatinine. Do not change any prescription over a lab number; ask your doctor.
Which equation your lab uses. NIDDK notes eGFR is calculated using estimating equations that may not always be precise.
Creatinine-only testing when a more precise answer is needed. NIDDK reports the combined creatinine–cystatin C equation gives higher accuracy and less bias than creatinine alone, which matters most when eGFR sits near a decision point.
Timing — a single draw. KDIGO (2024) uses creatinine-based eGFR as the initial test, with further testing when that estimate is expected to be inaccurate.
Questions to Ask Your Doctor About This Result
"Looking at my result alongside my other labs and my history, what does this number suggest to you?"
"Do I have any earlier GFR results on file, and has this number changed over time?"
"What is the next test or monitoring step — a repeat eGFR, a urine albumin-creatinine ratio, or a cystatin C-based estimate — and when should it happen?"
"Could my muscle mass, a recent illness, or anything I take be affecting this estimate?"
"Which equation does this lab use, and how precise is it likely to be for someone like me?"
"What symptoms would mean I should call you the same day rather than wait for the next test?"
"At what point would you refer me to a kidney specialist?"
Frequently asked questions
Does one low eGFR mean I have chronic kidney disease?
Not by itself — the National Kidney Foundation describes chronic kidney disease as kidney damage present for at least 3 months, and KDIGO (2024) establishes that duration by reviewing past or repeat GFR measurements. A single reading can be shifted by illness, hydration or muscle mass. What your result means is a question for your doctor, who has your full history and other results.{""}
Why is my number called "estimated" GFR?
Because the lab calculates it from blood creatinine plus age and sex rather than measuring filtration directly (MedlinePlus, undated). NIDDK notes the equations were developed from research study populations and are often less accurate when applied to one individual. How much weight to put on your specific figure is for your doctor, who has your full history and other results.
What is the cystatin C test I have seen mentioned?
Cystatin C is a second blood marker that can be combined with creatinine in an eGFR equation. NIDDK reports the combined creatinine–cystatin C equation gives higher accuracy and less bias than creatinine alone, which matters particularly when a result sits close to a decision point. Whether it is worth adding in your case is a decision for your doctor, who has your full history and other results.
Does the urine test matter if my eGFR is in the normal band?
It can. The National Kidney Foundation describes stage 1 CKD as possible kidney damage, such as protein in the urine, alongside normal kidney function, so urine findings carry information the blood number does not. How the two results fit together should be reviewed by your doctor, who has your full history and other results.
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