eGFR (CKD-EPI 2021) Calculator

eGFR (CKD-EPI 2021) Calculator for Nephrology. CKD assessment also needs chronicity and markers such as albuminuria. Drug dosing should follow the relevant label and specified kidney-function method; indexed eGFR is not automatically Cockcroft-Gault clearance.

Clinical learning case

Check the equation before interpreting a boundary result

Fictional teaching case. Not an individual treatment recommendation.

A 62-year-old woman has serum creatinine 1.3 mg/dL, with stable recent measurements. A handover describes her eGFR as about 44. Reproduce the 2021 creatinine-only CKD-EPI calculation before copying that value into the record.

  1. For this equation, the female creatinine breakpoint is 0.7 mg/dL. The ratio 1.3 / 0.7 is 1.8571, which is above one; the minimum term therefore equals one.
  2. Calculate 142 x (1.3 / 0.7)^(-1.200) x 0.9938^62 x 1.012 = approximately 46.5 mL/min/1.73 m2.
  3. The handover's value of 44 is not reproduced by these inputs and this equation. Check which equation, age, units and sample were used instead of averaging the two numbers.

Clinical reasoning

An estimate is not a measured filtration rate. The 2021 model does not use race and this tool uses creatinine, not the combined creatinine-cystatin C equation. A different biomarker or equation may produce a different estimate without either laboratory having made an arithmetic error. NIDDK notes that combined-marker estimation is more accurate and is particularly useful near a clinical decision boundary.

Error to avoid

The unit mL/min/1.73 m2 includes body-surface-area indexing. Do not silently relabel it mL/min or substitute it for Cockcroft-Gault clearance. Record the equation name beside the result so a later clinician can compare like with like.

Does a second creatinine result from an evolving acute illness make this a reliable real-time filtration monitor?

No. Rapidly changing creatinine undermines steady-state estimation. Assess the acute illness and serial findings rather than treating the displayed eGFR as an immediate measurement of kidney filtration.

Example documentation

CKD-EPI 2021 creatinine-only eGFR approximately 46.5 mL/min/1.73 m2; age 62, female coefficient, creatinine 1.3 mg/dL. Sample timing and stability checked. Equation and units retained for comparison.

Sources for this lesson

Source check: 2026-09-07. Editorial content by Quick Medical Calculator. Independent clinical sign-off is not recorded for this lesson.

For shared guidance on choosing a tool and documenting results, read the clinical calculator workflow.

How this calculator works

The 2021 CKD-EPI creatinine equation uses standardized serum creatinine in mg/dL, age and the equation's sex coefficient, without a race multiplier. Output is indexed to 1.73 m2.

When to use this calculator

Use for adult kidney-function estimation when creatinine is reasonably stable. Where accuracy affects an important decision, consider creatinine-cystatin C estimation or measured GFR as appropriate.

Inputs used

  • Serum creatinine
  • Age
  • Sex

Clinical interpretation

CKD assessment also needs chronicity and markers such as albuminuria. Drug dosing should follow the relevant label and specified kidney-function method; indexed eGFR is not automatically Cockcroft-Gault clearance.

Worked example

For a 62-year-old woman with creatinine 1.3 mg/dL, the equation gives 46.49 mL/min/1.73 m2. This lies in G3a; one measurement does not establish chronic kidney disease.

Limitations and safety notes

Acute creatinine changes, unusual muscle mass and other non-GFR determinants can distort the estimate. The tool does not calculate cystatin-C or combined equations. Its GFR category is not an instruction to start dialysis.

Frequently asked questions

Is the estimate usually within 10% of measured GFR?

No such accuracy is promised. NIDDK reports P30, the proportion within 30%, rather than an individual error bound.

Does 46.49 establish CKD today?

No. Review earlier results, urine findings and clinical context to establish persistence or other evidence of chronic disease.

References

  • NIDDK. eGFR Equations for Adults. https://www.niddk.nih.gov/research-funding/research-programs/kidney-clinical-research-epidemiology/laboratory/glomerular-filtration-rate-equations/adults
  • KDIGO. 2024 Clinical Practice Guideline for the Evaluation and Management of CKD. https://kdigo.org/wp-content/uploads/2024/03/KDIGO-2024-CKD-Guideline.pdf

Editorial review and citation methodology

Maintained by the Quick Medical Calculator Editorial Team. Content record date: September 7, 2026. A content date is not evidence of independent clinical review. Individual clinical sign-off is not recorded on this page.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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