CalculatorsKidneys and electrolyteseGFR calculator
eGFR calculator
Estimate how well your kidneys filter from one creatinine result, with the equation US labs now use.
80mL/min/1.73 m²
G2
60 to 89 is KDIGO stage G2. Common with age, and not kidney disease on its own unless there are other signs such as protein in the urine.
- Equation
- CKD-EPI 2021No race term
See the working
eGFR = 142 × min(Cr/κ, 1)^α × max(Cr/κ, 1)^−1.200 × 0.9938^age × 1.012κ = 0.7, α = -0.241, Cr = 0.90 mg/dL, age = 45= 80.3Kidney disease is only diagnosed when a change lasts three months or more.
What eGFR tells you
GFR is how much blood your kidneys filter each minute. It's hard to measure directly, so labs estimate it from creatinine, a waste product of muscle, along with your age and sex.
The 2021 CKD-EPI equation removed the race term the older one used, and it's what US kidney societies recommend.
When the number can mislead
Creatinine comes from muscle. Very muscular people, and people eating a lot of meat or taking creatine, can read lower than they really are. Very frail people, or anyone who has lost a lot of muscle, can read higher.
If that might be you, a cystatin C test is the usual next step, since it doesn't depend on muscle. And one low result isn't kidney disease: it has to last three months.
Questions
What's a normal eGFR?
90 or above is KDIGO stage G1. It falls slowly with age, and 60 to 89 alone isn't kidney disease unless there's another sign, such as protein in the urine.
Does creatine affect it?
It can. Creatine raises creatinine without harming the kidneys, which can make eGFR read low. Mention it to whoever reads your results.
Can this be used for dosing medicines?
Not from here. Doses are for your doctor and pharmacist, who may use other measures.
Is it valid under 18?
No. This equation is for adults, and the calculator takes 18 and over.
Sources
- Inker LA et al. New creatinine- and cystatin C-based equations to estimate GFR without race. NEJM, 2021.
- KDIGO 2024 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney International, 2024.
Written by LifeFrom from the sources above, and not yet reviewed by a clinician. An estimate for your own understanding: it doesn't diagnose or treat anything, and it doesn't replace your doctor.
