Medical AIeGFR CKD-EPI 2021 creatinine calculator
The 2021 CKD-EPI creatinine equation estimates glomerular filtration rate from serum creatinine, age, and sex, dropping the race coefficient used in earlier versions. The result is reported per 1.73m2 of body surface area and maps onto the KDIGO GFR categories used to stage chronic kidney disease.
How to measure each input
- Serum creatinine
- Use a standardised, isotope-dilution-mass-spectrometry (IDMS) traceable assay. If your lab reports umol/L, the calculator converts to mg/dL by dividing by 88.4.
- Age
- Current age in years. The 2021 equation was developed and validated in adults; do not apply it to children, who have their own equations.
- Sex
- Enter sex as used in the published coefficients (separate kappa and alpha terms, plus a 1.012 multiplier for females).
Interpretation
| Band | Meaning |
|---|---|
| G1, >= 90 (normal or high) | GFR is normal or high. This stages as CKD only if a marker of kidney damage (for example albuminuria or structural disease) is also present for at least 3 months. |
| G2, 60 to 89 (mildly decreased) | Mildly decreased GFR. As with G1, this is CKD only when accompanied by a marker of kidney damage. A mild reduction is common with age alone. |
| G3a, 45 to 59 (mild to moderate) | Mildly to moderately decreased GFR. Assess albuminuria, review nephrotoxic and renally-cleared drugs, and monitor. Combine with albuminuria (A stage) for full KDIGO risk. |
| G3b, 30 to 44 (moderate to severe) | Moderately to severely decreased GFR. Higher risk of progression and complications; consider nephrology input and management of anaemia, bone-mineral, and cardiovascular risk. |
| G4, 15 to 29 (severely decreased) | Severely decreased GFR. Refer to nephrology, plan for kidney-replacement options, and review all drug dosing. Avoid nephrotoxins. |
| G5, < 15 (kidney failure) | Kidney failure. Dialysis or transplantation is usually required if not already established. Urgent nephrology management. |
Pitfalls, exclusions and caveats
- eGFR assumes a steady state. It is invalid when creatinine is changing rapidly, as in acute kidney injury; in that setting trend the creatinine instead.
- Extremes of muscle mass distort the estimate: high muscle mass or creatine supplements over-estimate creatinine (under-estimate GFR), while low muscle mass, amputation, cirrhosis, or cachexia under-estimate creatinine (over-estimate GFR).
- Some drug labels and dosing references were developed with Cockcroft-Gault creatinine clearance, not BSA-indexed eGFR. For dosing decisions check which estimate the reference expects, and consider de-indexing eGFR to the individual's body surface area.
- The result is indexed to 1.73m2 of body surface area, so it is not the patient's absolute clearance; this matters at extremes of body size.
- A single eGFR does not diagnose CKD. KDIGO requires the abnormality to persist for at least 3 months and to be combined with albuminuria (the A stage) for full risk classification.
eGFR = 142 x min(Scr/k, 1)^a x max(Scr/k, 1)^-1.200 x 0.9938^age x 1.012 (if female). Scr in mg/dL. Female: k = 0.7, a = -0.241. Male: k = 0.9, a = -0.302. Result in mL/min/1.73m^2.The CKD-EPI 2021 creatinine equation was published by Inker et al. (2021). This implementation is an educational tool and is not affiliated with the original authors, the CKD-EPI collaboration, or KDIGO.
Frequently asked
Why does the 2021 CKD-EPI equation drop the race coefficient?
Earlier CKD-EPI equations multiplied results by a fixed factor for Black patients, which was poorly justified biologically and could mask kidney disease. The 2021 refit removed race entirely and was adopted by major nephrology bodies to make estimates race-free.
What is a normal eGFR?
An eGFR of 90 mL/min/1.73m2 or above is in the normal-or-high range (KDIGO G1). Values of 60 to 89 (G2) are mildly reduced and can be normal for age. eGFR only diagnoses CKD when an abnormality persists for at least 3 months, ideally alongside albuminuria.
Can I use this eGFR for drug dosing?
With caution. Many renal-dosing references were built on Cockcroft-Gault creatinine clearance, not BSA-indexed eGFR. Check what the specific drug label expects, and consider de-indexing the eGFR to the patient's body surface area for very small or very large patients.
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