CKD-EPI eGFR Calculator

Estimate glomerular filtration rate using the 2021 CKD-EPI creatinine equation (race-free). Classify CKD stage and guide monitoring, referral, and management decisions.

Clinical Tool· Nephrology· Internal Medicine· Primary Care

Calculate eGFR

Enter serum creatinine, age, and sex to estimate GFR using the 2021 CKD-EPI creatinine equation. This is the race-free equation recommended by KDIGO and endorsed by the NKF-ASN Task Force. Toggle between conventional (mg/dL) and SI (µmol/L) units for creatinine.

Creatinine Units

Required Values

Serum Creatinine mg/dL · Normal: 0.7–1.3 (M), 0.6–1.1 (F)

Age Years · 18–120

Sex Biological sex at birth

G5 (<15) G4 G3b G3a G2 G1 (≥90)

Important

eGFR is an estimation and should not be used to make clinical decisions in isolation. It is less reliable at extremes of body size, in acute kidney injury, during pregnancy, and in patients with unusual dietary intake or muscle mass. CKD diagnosis requires evidence of kidney damage or decreased GFR persisting for ≥ 3 months — a single eGFR value is insufficient.

Understanding eGFR

The glomerular filtration rate (GFR) is the gold-standard measure of kidney function. It reflects the total volume of plasma filtered by the glomeruli per unit time, normally approximately 120 mL/min/1.73 m² in healthy young adults. Directly measuring GFR requires exogenous filtration markers (inulin, iohexol) — impractical for routine use. Instead, we estimate GFR from endogenous markers, principally serum creatinine.

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) developed creatinine-based equations that are more accurate than the older MDRD equation, particularly at higher GFR values (> 60 mL/min/1.73 m²). In 2021, the NKF-ASN Task Force recommended a new race-free CKD-EPI equation, removing the race coefficient to address concerns about the biological validity and clinical equity implications of race-based adjustments.

2021 CKD-EPI Equation

eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^Age × 1.012 [if female]

Where κ = 0.7 (female) or 0.9 (male), and α = −0.241 (female) or −0.302 (male). Scr is serum creatinine in mg/dL. No race coefficient is used.

Worked Example

55-year-old male, Scr = 1.4 mg/dL

κ = 0.9, α = −0.302, Scr/κ = 1.4/0.9 = 1.556

min(1.556, 1) = 1 → 1^−0.302 = 1.0

max(1.556, 1) = 1.556 → 1.556^−1.200 = 0.594

142 × 1.0 × 0.594 × 0.9938⁵⁵ = 142 × 0.594 × 0.711 = ~60 mL/min/1.73 m²

2021 vs. 2009 equation: The 2021 CKD-EPI equation removes the race coefficient present in the original 2009 equation. This means eGFR values may be lower for patients previously categorised as Black and slightly higher for others compared to the 2009 equation. KDIGO 2024 guidelines and major nephrology societies endorse the 2021 race-free equation for routine clinical use.

CKD Staging & Classification

Chronic kidney disease is classified by both GFR category (G1–G5) and albuminuria category (A1–A3). Both dimensions are needed for prognosis and management — a patient with eGFR 50 and A1 albuminuria has a very different risk profile from one with eGFR 50 and A3 albuminuria. CKD diagnosis requires abnormalities persisting for ≥ 3 months.

GFR Categories

GFR Category	eGFR (mL/min/1.73 m²)	Description	Clinical Implication
G1	≥ 90	Normal or high	CKD only if other markers of kidney damage present (albuminuria, structural abnormality)
G2	60–89	Mildly decreased	CKD only if other markers of kidney damage present; common in elderly without pathology
G3a	45–59	Mildly to moderately decreased	Monitor progression, adjust renally cleared medications, assess cardiovascular risk
G3b	30–44	Moderately to severely decreased	Screen for complications (anaemia, mineral-bone disease, acidosis); consider nephrology referral
G4	15–29	Severely decreased	Nephrology referral essential; prepare for renal replacement therapy; manage complications actively
G5	< 15	Kidney failure	Dialysis or transplant planning; multidisciplinary care; advance care planning discussions

Albuminuria Categories

Category	ACR (mg/g)	Description
A1	< 30	Normal to mildly increased
A2	30–300	Moderately increased (formerly “microalbuminuria”)
A3	> 300	Severely increased (formerly “macroalbuminuria”)

Clinical Pearl

An eGFR of 60–89 mL/min/1.73 m² alone does not constitute CKD in the absence of other markers of kidney damage. Many healthy older adults have mildly reduced eGFR as part of normal ageing. KDIGO requires evidence of structural or functional abnormality (albuminuria, haematuria, electrolyte disturbances from tubular disorders, histological abnormalities, imaging abnormalities, or history of kidney transplantation) to diagnose CKD at G1 or G2.

Clinical Details & Complications of CKD

As eGFR declines, a cascade of metabolic and systemic complications develops. Recognising these complications at the appropriate CKD stage allows early intervention and slows disease progression. The following accordions summarise the key complications and their management triggers.

Cardiovascular Risk

CKD is an independent cardiovascular risk factor. Patients with CKD G3 and below have a higher risk of death from cardiovascular disease than of progressing to dialysis. Mechanisms include accelerated atherosclerosis, vascular calcification driven by disordered calcium-phosphate metabolism, volume overload, left ventricular hypertrophy, and uraemic cardiomyopathy.

Cardiovascular risk assessment should begin at CKD G3a. Blood pressure targets are typically < 120 mmHg systolic (per SPRINT and KDIGO 2021). SGLT2 inhibitors (dapagliflozin, empagliflozin) and finerenone have demonstrated cardiorenal protective benefits beyond glucose control and are now recommended in CKD with albuminuria regardless of diabetes status.

Anaemia of CKD

Renal anaemia typically becomes clinically apparent at CKD G3b–G4 and is primarily caused by decreased erythropoietin (EPO) production by peritubular interstitial cells. Iron deficiency (absolute and functional) is a common co-contributor and should be assessed first. KDIGO recommends checking haemoglobin annually from CKD G3a and more frequently from G3b.

Iron supplementation (oral or IV) is first-line when transferrin saturation is < 20% or ferritin is < 100 ng/mL (non-dialysis) or < 200 ng/mL (dialysis). Erythropoiesis-stimulating agents (ESAs) are used when Hb is < 10 g/dL after iron repletion, targeting 10–11.5 g/dL — not normalisation, which is associated with increased cardiovascular events (CHOIR, CREATE, TREAT trials).

CKD–Mineral and Bone Disorder (CKD-MBD)

As GFR declines (typically G3b and below), phosphate excretion becomes impaired, leading to hyperphosphataemia, secondary hyperparathyroidism, and vitamin D deficiency (decreased 1,25-dihydroxyvitamin D production). The combination drives renal osteodystrophy and vascular calcification.

Monitor calcium, phosphate, PTH, and 25-hydroxyvitamin D from CKD G3b. Dietary phosphate restriction and phosphate binders (calcium-based or non-calcium-based) are used when phosphate rises above the normal range. Active vitamin D analogues (calcitriol, alfacalcidol) may be needed for secondary hyperparathyroidism. Cinacalcet or parathyroidectomy is reserved for severe, refractory hyperparathyroidism.

Metabolic Acidosis

Metabolic acidosis in CKD occurs due to impaired ammoniagenesis and reduced net acid excretion. It typically develops at CKD G4–G5 (eGFR < 30 mL/min/1.73 m²) but can appear earlier. Chronic metabolic acidosis accelerates muscle catabolism, promotes bone demineralisation, and may hasten CKD progression.

KDIGO recommends maintaining serum bicarbonate ≥ 22 mEq/L. Oral sodium bicarbonate supplementation (0.5–1 mEq/kg/day) is first-line. Veverimer, a non-absorbed oral hydrochloric acid binder, is an emerging option. Dietary approaches (increased fruit and vegetable intake) may also help buffer acid load in earlier stages.

Hyperkalaemia

Potassium homeostasis is maintained until late CKD (typically G4–G5), but patients on RAAS inhibitors, SGLT2 inhibitors, or MRAs may develop hyperkalaemia earlier. Chronic hyperkalaemia is a common reason for premature discontinuation of cardioprotective RAAS blockade — a decision that may paradoxically worsen long-term outcomes.

Newer potassium binders (patiromer, sodium zirconium cyclosilicate) can enable continued use of RAAS inhibitors by managing chronic hyperkalaemia. Dietary potassium restriction is recommended for recurrent or severe hyperkalaemia (K⁺ > 5.5 mEq/L).

Special Populations & Considerations

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Elderly Patients (≥ 65 years)

GFR physiologically declines with age at approximately 1 mL/min/year after age 40. An eGFR of 60–75 in an 80-year-old may represent normal ageing rather than pathological CKD. KDIGO emphasises that age-related GFR decline alone, without albuminuria or structural abnormality, should not be automatically labelled as CKD. Clinical judgement is essential to avoid over-diagnosis and unnecessary interventions.

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Extremes of Muscle Mass

Creatinine is a byproduct of muscle metabolism. In patients with high muscle mass (bodybuilders, athletes), serum creatinine may be elevated without true kidney impairment, leading to falsely low eGFR. Conversely, in sarcopenic, cachectic, or amputee patients, low creatinine production yields misleadingly high eGFR values that overestimate true kidney function. Cystatin C–based equations or measured GFR should be considered in these populations.

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Pregnancy

GFR increases by approximately 50% during pregnancy due to increased renal plasma flow and cardiac output, reaching a peak in the second trimester. Serum creatinine therefore falls (normal: ~0.4–0.7 mg/dL). A “normal” non-pregnant creatinine of 1.0 mg/dL may represent impaired function in pregnancy. Creatinine-based eGFR equations are not validated in pregnancy and should not be used — clinical assessment and measured creatinine trends are preferred.

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Acute Kidney Injury (AKI)

eGFR equations assume a steady-state creatinine level. During AKI, creatinine is actively rising and has not yet equilibrated — eGFR in this context is unreliable and will significantly overestimate true kidney function. In AKI, follow creatinine trends, urine output, and clinical status rather than eGFR. Reassess with eGFR after creatinine has stabilised post-recovery.

When to consider cystatin C: KDIGO recommends confirmatory cystatin C–based eGFR (CKD-EPI 2021 creatinine-cystatin C equation) when creatinine-based eGFR may be inaccurate — specifically in patients with extremes of body habitus, unusual diet (vegetarian, creatine supplements), or when the clinical picture does not match the creatinine-based eGFR. Cystatin C is less influenced by muscle mass but is affected by thyroid function, glucocorticoids, obesity, and inflammation.

CKD Management by Stage

CKD management is stage-dependent and cumulative — interventions appropriate at earlier stages continue alongside new ones added as eGFR declines. The following framework reflects KDIGO 2024 and recent landmark trial evidence.

All Stages — Foundational Measures

These interventions apply from the point of CKD diagnosis regardless of stage: blood pressure control targeting < 120/80 mmHg (systolic target per SPRINT); maximally tolerated RAAS inhibition (ACEi or ARB) in patients with albuminuria (A2 or A3); cardiovascular risk factor management (statin/ezetimibe per SHARP trial for CKD G3–G5 not on dialysis); smoking cessation; weight management; and regular monitoring of eGFR, albuminuria, electrolytes, and haemoglobin.

SGLT2 inhibitors (dapagliflozin, empagliflozin) are now recommended for patients with CKD and eGFR ≥ 20 mL/min/1.73 m² with albuminuria (ACR ≥ 200 mg/g), and may be considered at lower albuminuria thresholds (ACR 30–200 mg/g) based on DAPA-CKD and EMPA-KIDNEY trial data. Finerenone, a non-steroidal MRA, provides additional cardiorenal benefit in patients with type 2 diabetes and CKD (FIDELIO-DKD, FIGARO-DKD).

G3a–G3b — Complication Screening

At G3a (eGFR 45–59), begin screening for CKD-related complications: check haemoglobin, calcium, phosphate, PTH, bicarbonate, and potassium at least annually. Adjust renally cleared medications (metformin dose adjustment at eGFR < 45, contraindicated < 30; DOAC dose adjustments; NSAID avoidance). Review nephrotoxic medications and contrast exposure protocols.

At G3b (eGFR 30–44), increase monitoring frequency (every 3–6 months). Consider nephrology referral if eGFR is declining rapidly (> 5 mL/min/year), there is persistent significant albuminuria (A3), or the aetiology of CKD is uncertain. Begin patient education about disease trajectory and potential future renal replacement therapy options.

G4 — Nephrology Referral & Preparation

All patients with CKD G4 (eGFR 15–29) should be under nephrology care. Key actions include: active management of anaemia, CKD-MBD, acidosis, and hyperkalaemia; vaccination (hepatitis B, pneumococcal, influenza); vascular access planning for potential haemodialysis (AVF creation at least 6 months before anticipated need); transplant evaluation for eligible patients; and advance care planning discussions including conservative care options.

Avoid nephrotoxins rigorously. Monitor eGFR every 1–3 months. Dietary review with renal dietitian (potassium, phosphate, protein, sodium restriction). Adjust all medications for reduced clearance.

G5 — Kidney Failure & Renal Replacement Therapy

CKD G5 (eGFR < 15) represents kidney failure. Timing of dialysis initiation is guided by symptoms (uraemia, volume overload, refractory hyperkalaemia, pericarditis) rather than a fixed eGFR threshold — the IDEAL trial demonstrated no benefit from early dialysis initiation. Options include haemodialysis (in-centre or home), peritoneal dialysis, pre-emptive kidney transplantation, and conservative (non-dialytic) management for selected patients.

Pre-emptive transplantation (before dialysis initiation) offers the best outcomes when a suitable donor is available. For patients electing conservative care, focus shifts to symptom management, quality of life, and palliative support.

Common Pitfalls & Limitations

Using eGFR During Acute Kidney Injury

Creatinine-based eGFR equations assume a steady-state creatinine concentration. During AKI, creatinine is actively rising (or falling during recovery) and has not yet reached equilibrium. In this setting, eGFR dramatically overestimates true GFR during creatinine rise and underestimates during recovery. Clinical decisions in AKI should be based on creatinine trends, urine output, and clinical assessment — not eGFR. Reserve eGFR for reassessment once creatinine has stabilised post-AKI.

Ignoring Muscle Mass Effects on Creatinine

Creatinine production is proportional to muscle mass. A serum creatinine of 0.6 mg/dL in a frail 80-year-old with minimal muscle mass may represent an actual GFR far lower than the eGFR suggests. Conversely, a bodybuilder with a creatinine of 1.5 mg/dL may have entirely normal kidney function. This is the most common reason eGFR is clinically misleading. When muscle mass is clearly unusual, consider cystatin C–based eGFR or measured GFR for drug dosing and clinical decisions.

Diagnosing CKD From a Single eGFR

A single eGFR below 60 does not establish CKD. KDIGO requires abnormalities (decreased GFR < 60 or markers of kidney damage) to be present for at least 3 months to meet the diagnostic threshold. Transient drops in eGFR are common — intercurrent illness, dehydration, medications (ACEi/ARB initiation, NSAID use), and laboratory variability can all cause short-term fluctuations. Always confirm with a repeat measurement at least 90 days later before labelling a patient with CKD.

Overlooking Albuminuria in Risk Assessment

GFR and albuminuria are independent predictors of outcomes. Two patients with the same eGFR (e.g., 45 mL/min/1.73 m²) can have vastly different prognoses depending on their albuminuria status — A1 carries moderate risk, while A3 carries very high risk for progression and cardiovascular events. The KDIGO heat map combines both dimensions for risk stratification, yet albuminuria is frequently omitted from initial CKD assessment in primary care. Always check the urine albumin-to-creatinine ratio (ACR) alongside eGFR.

Using an Outdated Equation (MDRD or Cockcroft-Gault)

The MDRD equation, while historically important, systematically underestimates GFR in patients with near-normal kidney function (eGFR > 60), leading to over-diagnosis of CKD. The Cockcroft-Gault equation estimates creatinine clearance (not GFR), is not standardised to body surface area, and uses an outdated creatinine assay methodology. Both have been superseded by the CKD-EPI equations. For drug dosing, most modern pharmacokinetic studies use CKD-EPI — though some older drug labels still reference Cockcroft-Gault, requiring clinical judgement.

Quick Reference Summary

≥ 90 Normal eGFR
(mL/min/1.73 m²)

≥ 3 mo Duration required
to diagnose CKD

< 30 ACR (mg/g) threshold
for normal (A1)

5 mL/yr Rapid decline threshold
requiring referral

CKD Stage	eGFR	Key Action	Monitoring Frequency
G1–G2	≥ 60	Identify cause; RAAS blockade if albuminuria; CV risk management	Annually
G3a	45–59	Complication screening; medication adjustment; consider SGLT2i	Every 6–12 months
G3b	30–44	Nephrology referral if rapid decline or A3; active complication management	Every 3–6 months
G4	15–29	Nephrology essential; RRT preparation; access planning; transplant evaluation	Every 1–3 months
G5	< 15	Dialysis/transplant/conservative care decision; symptom management	Every 1–2 months

The Golden Rule: eGFR is only half the picture — always check urine albumin-to-creatinine ratio (ACR) alongside eGFR. The combination of GFR category and albuminuria category determines prognosis, referral timing, and treatment intensity far more accurately than either alone.

Disclaimer & References

Disclaimer

For Educational Purposes Only. This calculator and the accompanying clinical information are intended as educational tools for healthcare professionals. They do not replace clinical judgement. Results should be interpreted in the full clinical context. Lab reference ranges vary by institution — verify with your own laboratory. Drug dosages should be confirmed against current prescribing information.

References

Inker LA, Eneanya ND, Coresh J, et al. New creatinine- and cystatin C–based equations to estimate GFR without race. New England Journal of Medicine. 2021;385(19):1737-1749. DOI: 10.1056/NEJMoa2102953
Levey AS, Stevens LA, Schmid CH, et al. A new equation to estimate glomerular filtration rate. Annals of Internal Medicine. 2009;150(9):604-612. DOI: 10.7326/0003-4819-150-9-200905050-00006
Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney International. 2024;105(4S):S117-S314. DOI: 10.1016/j.kint.2023.10.018
Delgado C, Baweja M, Crews DC, et al. A unifying approach for GFR estimation: recommendations of the NKF-ASN Task Force on reassessing the inclusion of race in diagnosing kidney disease. American Journal of Kidney Diseases. 2022;79(2):268-288.e1. DOI: 10.1053/j.ajkd.2021.08.003
Heerspink HJL, Stefánsson BV, Correa-Rotter R, et al. Dapagliflozin in patients with chronic kidney disease. New England Journal of Medicine. 2020;383(15):1436-1446. DOI: 10.1056/NEJMoa2024816
The EMPA-KIDNEY Collaborative Group. Empagliflozin in patients with chronic kidney disease. New England Journal of Medicine. 2023;388(2):117-127. DOI: 10.1056/NEJMoa2204233
Bakris GL, Agarwal R, Anker SD, et al. Effect of finerenone on chronic kidney disease outcomes in type 2 diabetes. New England Journal of Medicine. 2020;383(23):2219-2229. DOI: 10.1056/NEJMoa2025845
Cooper BA, Branley P, Bulfone L, et al. A randomized, controlled trial of early versus late initiation of dialysis (IDEAL). New England Journal of Medicine. 2010;363(7):609-619. DOI: 10.1056/NEJMoa0909753
Barratt J, Haynes R, Lewis D, et al. The SHARP trial: effects of lowering LDL cholesterol among patients with CKD. The Lancet. 2011;377(9784):2181-2192. DOI: 10.1016/S0140-6736(11)60739-3
Stevens PE, Levin A; Kidney Disease: Improving Global Outcomes Chronic Kidney Disease Guideline Development Work Group Members. Evaluation and management of chronic kidney disease: synopsis of the kidney disease: improving global outcomes 2012 clinical practice guideline. Annals of Internal Medicine. 2013;158(11):825-830. DOI: 10.7326/0003-4819-158-11-201306040-00007