Nephrology

Estimated Glomerular Filtration Rate — CKD-EPI 2021 Equation

3 inputsNephrology

Estimate kidney function using the 2021 CKD-EPI creatinine equation.

Calculate

eGFR (CKD-EPI 2021) calculator

Result

91.7mL/min/1.73m²

G1 — Normal

How to use it

1
Enter serum creatinine (mg/dL). Fasting not required. Acute illness can transiently lower eGFR.
2
Age and sex. CKD-EPI 2021 removes race variable as per NKF/ASN joint task force.
3
CKD staging needs two values ≥3 months apart. Single low eGFR could be AKI.

When to use it

Calculate eGFR in all patients with potential CKD, diabetes, hypertension, or heart failure. Essential for drug dosing decisions. Required before initiating or continuing metformin, SGLT2 inhibitors, NOACs, low-molecular-weight heparin, and many nephrotoxic agents.

CKD diagnosis and staging: eGFR + ACR defines CKD stage (KDIGO 2024).
Drug dosing: Most renal drug dose adjustments reference eGFR.
Contrast safety: eGFR < 30: nephrology consult before contrast CT.

About the score

The estimated Glomerular Filtration Rate (eGFR) using the 2021 CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) creatinine equation is the standard method for assessing kidney function in clinical practice worldwide. The 2021 equation removed race as a variable from the original 2009 CKD-EPI formula to improve equity in CKD staging and organ transplant eligibility. eGFR is the cornerstone of KDIGO CKD staging, guides dosage adjustments for renally cleared drugs (including NOACs, antibiotics, and metformin), and determines eligibility for SGLT2 inhibitors — which are now indicated for CKD regardless of diabetes status per KDIGO 2024 guidelines.

Scoring criteria

Serum creatinine (µmol/L or mg/dL)Primary variable in CKD-EPI equation: Continuous
Age (years): Continuous
Sex (male/female): Categorical
(Optional) Serum cystatin CCKD-EPI creatinine-cystatin C equation provides more accurate estimation: Continuous

Score interpretation

≥ 90 (G1)Normal or highCKD only if markers of kidney damage present (proteinuria, haematuria)
60–89 (G2)Mildly decreasedCKD if kidney damage markers present; monitor annually
45–59 (G3a)Mildly to moderately dec.CKD; nephrology referral not usually needed; check albuminuria to guide SGLT2i
30–44 (G3b)Moderately to severelyCKD; nephrology referral; metformin dose review
15–29 (G4)Severely decreasedNephrology referral for transplant/dialysis planning
< 15 (G5)Kidney failureRenal replacement therapy or conservative management

Guideline recommendation

KDIGO 2024 CKD Guideline: estimate GFR with a validated creatinine-based equation and use the same equation within a region; in the United States that is the 2021 CKD-EPI equation (NKF-ASN Task Force). An SGLT2 inhibitor is recommended for adults with CKD and eGFR ≥20 ml/min/1.73m² who have uACR ≥200 mg/g (≥20 mg/mmol) or heart failure (grade 1A). Metformin generally safe to eGFR ≥30 ml/min/1.73m².

KDIGO 2024Chronic Kidney Disease 2024

Clinical pearls

eGFR fluctuates — at least two measurements >90 days apart are needed to classify CKD (single low value may be acute).
Muscle mass affects creatinine-based eGFR — frail, sarcopenic, or vegan patients may have misleadingly high eGFR; cystatin C-based eGFR is more accurate in these groups.
The 2021 CKD-EPI equation (without race) replaced the 2009 equation — ensure your laboratory and clinical systems have adopted it.
eGFR <45 is the threshold for many drug dose adjustments — review all renally cleared drugs at this threshold.
Proteinuria (uACR) combined with eGFR provides better risk stratification than eGFR alone — the KDIGO heat map plots both axes.

Limitations

Creatinine-based eGFR is influenced by muscle mass, dietary protein, and tubular secretion of creatinine.
Less accurate at high eGFR values (>90 ml/min/1.73m²) where absolute GFR may differ significantly from estimated values.
Not validated for use during acute kidney injury — use absolute creatinine trends instead.

A reference for clinicians and students, not medical advice. A score supports a decision; it does not make one. Check every result against the patient in front of you and your local protocol.

At a glance

Specialty: Nephrology
Inputs: 3
Type: Formula
Guidelines from: KDIGO, NKF

Frequently asked questions

What is a normal eGFR level?

An eGFR ≥90 mL/min/1.73m² is considered normal kidney function (KDIGO G1 stage). Values of 60–89 represent mildly decreased function (G2). CKD is defined as eGFR <60 mL/min/1.73m² or evidence of kidney damage (such as proteinuria or haematuria) persisting for >3 months. A single low value may reflect acute injury rather than CKD.

When should I refer to nephrology based on eGFR?

KDIGO recommends nephrology referral for eGFR <30 mL/min/1.73m² (G4–G5), or for eGFR 30–44 (G3b) with a rapid rate of decline, significant proteinuria, or difficult-to-manage complications. Earlier referral (eGFR 45–59) is warranted if there are concerns about underlying cause or trajectory.

What is the difference between 2021 and 2009 CKD-EPI equations?

The 2021 CKD-EPI equation removed race as a variable. The original 2009 equation included a race coefficient that assigned Black patients a higher eGFR, which was found to perpetuate healthcare inequities. The NKF-ASN Task Force recommends the 2021 equation for all adults in the United States.