CKD-EPI 2021 eGFR Equation

Q: What does eGFR measure?

eGFR estimates how well the kidneys are filtering waste from the blood, expressed in mL/min/1.73 m².

Q: Why was the race variable removed from CKD-EPI?

The 2021 equation removed race because including it was not scientifically justified and contributed to health disparities in CKD detection.

Q: Is CKD-EPI better than MDRD?

Yes. CKD-EPI is more accurate at higher GFR values and is now the preferred equation in most guidelines.

Estimates glomerular filtration rate (eGFR) using the 2021 CKD-EPI creatinine equation.

Nephrology Internal MedicineEvidence-BasedUpdated 2026-08-06

Clinical decision-support tool for qualified healthcare professionals. Results are not a diagnosis and should not replace professional clinical judgment.

Clinical Notes

The 2021 CKD-EPI creatinine equation estimates glomerular filtration rate (eGFR) in mL/min/1.73 m² from serum creatinine, age, and sex. The 2021 equation removed the race coefficient, which was not scientifically justified and contributed to health disparities in CKD detection. eGFR is an estimate, not a directly measured GFR. It is most accurate in the range of 45–90 mL/min/1.73 m² and becomes less reliable at very high or very low GFR values, in extremes of muscle mass, in amputees, and during pregnancy. The equation assumes a stable, steady-state creatinine; do not use it during acute kidney injury (AKI) or when creatinine is rapidly changing. CKD staging based on eGFR (G1 through G5) requires confirmation of chronicity—repeat testing after at least 3 months is recommended before diagnosing chronic kidney disease. This calculator is not intended for medication dosing; many drug labels still require creatinine clearance from the Cockcroft-Gault equation. Always interpret eGFR alongside the patient’s clinical context, albuminuria status, and other markers of kidney damage.

Calculator Information

Specialty

Internal Medicine

📋 Reference Ranges

Normal Range

≥90 mL/min/1.73 m²

Reference ranges for this calculator
Classification	Range
G1: Normal or high	≥90
G2: Mildly decreased	60–89
G3a: Mild to moderate	45–59
G3b: Moderate to severe	30–44
G4: Severely decreased	15–29
G5: Kidney failure	<15

What This Calculator Measures

Estimates glomerular filtration rate (eGFR) using the 2021 CKD-EPI creatinine equation, which removed the race variable.

How to Use

Enter the patient's age, sex, and serum creatinine (mg/dL).
Use the most recent stable creatinine value.
Review the eGFR and CKD stage.
Repeat testing after 3 months to confirm chronicity before diagnosing CKD.

How the Calculation Works

The 2021 CKD-EPI creatinine equation estimates eGFR = 142 x min(Scr/k, 1)^alpha x max(Scr/k, 1)^-1.200 x 0.9938^age x 1.012 (female). Scr is serum creatinine in mg/dL; k is 0.7 (female) or 0.9 (male); alpha is -0.241 (female) or -0.302 (male). The race coefficient used in earlier equations was removed.

Variables Explained

Age

Age in years, entered into the 0.9938^age term so that eGFR declines with older age.

Sex

Biological sex, which sets the k and alpha constants and applies the 1.012 multiplier for females.

Serum Creatinine

Serum creatinine in mg/dL, the filtration marker that is divided by k (0.7 female, 0.9 male) before exponentiation.

Interpretation Guide

eGFR ≥90 is normal (G1). 60–89 is mildly decreased (G2). 45–59 is mild-to-moderate decrease (G3a). 30–44 is moderate-to-severe decrease (G3b). 15–29 is severely decreased (G4). <15 indicates kidney failure (G5).

Sex-specific interpretationAge-specific interpretation

Clinical Significance

eGFR is essential for CKD staging, drug dosing decisions, and monitoring kidney function over time. The 2021 CKD-EPI equation is the current standard recommended by KDIGO.

When It Is Useful

Routine estimation of kidney function
CKD staging per KDIGO guidelines
Monitoring progressive kidney disease
Initial kidney function assessment

When It Is Not Useful

Medication dosing without checking drug-specific guidance (Cockcroft-Gault may be required)
Acute kidney injury — use stable baseline creatinine
Extremes of muscle mass without clinical correlation
Pregnancy — use pregnancy-specific GFR estimation

Common Mistakes

Using the CKD-EPI result to adjust medication doses when the drug label requires Cockcroft-Gault creatinine clearance instead.
Applying the equation during acute kidney injury, when a rapidly changing creatinine breaks the steady-state assumption.
Diagnosing chronic kidney disease from a single low eGFR without repeating testing after at least 3 months to confirm chronicity.

Limitations

CKD-EPI is an estimate; it may be inaccurate in extremes of muscle mass, amputees, or pregnancy.
Do not use for medication dosing without checking drug-specific guidance.
Less accurate at very high or very low GFR values.
The 2021 equation does not include race, which improves equity but may differ from older equations in some populations.

Worked Example

A 65-year-old woman with diabetes has a serum creatinine of 1.1 mg/dL.

Inputs:

age: 65

sex: 2

creatinine: 1.1

Expected Result: eGFR ≈ 56 mL/min/1.73 m², which corresponds to CKD stage G3a (mild-to-moderate decrease). Repeat in 3 months to confirm chronicity.

Evidence & References

Source:: NKF / KDIGO
Reference:: Inker LA, et al. NEJM. 2021;385:1737-1749.

Inker LA, et al. NEJM. 2021.

References

Inker LA, et al. New Creatinine- and Cystatin C–Based Equations to Estimate GFR without Race. N Engl J Med. 2021;385:1737-1749. (Level I)
KDIGO 2024 Clinical Practice Guideline for CKD. (Guideline)

Frequently Asked Questions

What does eGFR measure?

eGFR estimates how well the kidneys are filtering waste from the blood, expressed in mL/min/1.73 m².

Why was the race variable removed from CKD-EPI?

The 2021 equation removed race because including it was not scientifically justified and contributed to health disparities in CKD detection.

Is CKD-EPI better than MDRD?

Yes. CKD-EPI is more accurate at higher GFR values and is now the preferred equation in most guidelines.

Disclaimer: This calculator is intended for educational and clinical decision support purposes only. eGFR is an estimate and should be interpreted alongside clinical context. It does not replace direct GFR measurement or clinical judgment.