eGFR Calculator (CKD-EPI 2009)
How to Use This Calculator
This eGFR calculator uses the CKD-EPI 2009 equation, recommended by NICE for UK clinical practice. Enter the patient’s age, sex, and serum creatinine level to receive an estimated glomerular filtration rate along with CKD staging and clinical recommendations.
- Patients must be 18 years or older (use paediatric equations for younger individuals)
- Creatinine values should be from a stable patient (not during acute kidney injury)
- Advise patients not to consume meat 12 hours before blood sampling
- Blood samples should reach the laboratory within 12 hours of collection
- No ethnicity adjustment is applied, following current UK guidance
CKD Stages
Chronic kidney disease is classified into five stages based on eGFR values and presence of kidney damage markers. Both eGFR and albuminuria (ACR) determine overall risk and management approach.
| Stage | Description | eGFR (mL/min/1.73m²) | Clinical Significance |
|---|---|---|---|
| G1 | Normal or high | ≥90 | Not CKD without other kidney damage evidence |
| G2 | Mildly decreased | 60-89 | Not CKD without other kidney damage evidence |
| G3a | Mild to moderate decrease | 45-59 | Mild to moderate reduction in kidney function |
| G3b | Moderate to severe decrease | 30-44 | Moderate to severe reduction in kidney function |
| G4 | Severely decreased | 15-29 | Severe reduction in kidney function |
| G5 | Kidney failure | <15 | Established kidney failure requiring renal replacement therapy consideration |
Albuminuria Classification
Albumin-to-creatinine ratio (ACR) measurements complement eGFR in assessing kidney disease severity and progression risk. Higher ACR levels indicate greater kidney damage and cardiovascular risk.
| Category | ACR (mg/mmol) | Description | Clinical Action |
|---|---|---|---|
| A1 | <3 | Normal to mildly increased | Annual monitoring if at risk |
| A2 | 3-29 | Moderately increased | Consider RAAS inhibitors, SGLT2 inhibitors |
| A3 | ≥30 | Severely increased | Specialist referral, aggressive treatment |
CKD-EPI 2009 Equation
The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) 2009 formula provides more accurate eGFR estimates than the older MDRD equation, particularly at higher levels of kidney function. NICE specifically recommends this equation for UK practice without ethnicity adjustment.
eGFR = 144 × (SCr/0.7)^(-0.329) × 0.993^Age
For females with creatinine >62 µmol/L (>0.7 mg/dL):
eGFR = 144 × (SCr/0.7)^(-1.209) × 0.993^Age
For males with creatinine ≤80 µmol/L (≤0.9 mg/dL):
eGFR = 141 × (SCr/0.9)^(-0.411) × 0.993^Age
For males with creatinine >80 µmol/L (>0.9 mg/dL):
eGFR = 141 × (SCr/0.9)^(-1.209) × 0.993^Age
Where SCr represents serum creatinine in mg/dL and Age is in years. The result is expressed in mL/min/1.73m².
Clinical Interpretation
When eGFR May Be Inaccurate
The CKD-EPI equation assumes stable creatinine levels and may not provide reliable estimates in certain populations:
- Acute kidney injury with rapidly changing creatinine
- Patients receiving dialysis
- Extremes of body composition (severe malnutrition, bodybuilders, morbid obesity)
- Limb amputations affecting muscle mass
- Pregnancy (equation not validated)
- Children under 18 years (use paediatric equations)
- Patients from certain ethnic backgrounds (limited validation data in UK populations)
Monitoring Recommendations
Management Thresholds
NICE provides specific treatment recommendations based on ACR levels for patients with CKD:
| ACR (mg/mmol) | Recommendation |
|---|---|
| >3 | Abnormal, defines CKD G1/G2. Start ACE inhibitor or ARB if diabetic. Consider SGLT2 inhibitor for type 2 diabetes if eGFR ≥20-25 |
| >22.6 | Start SGLT2 inhibitor in non-diabetic CKD if eGFR ≥20-25 |
| >30 | Favour RAAS inhibitors if hypertensive |
| >70 | Consider RAAS inhibitor and lower BP target (130/80 mmHg). Specialist referral unless diabetic with optimised treatment |
| >300 | Nephrotic range proteinuria. Mandatory specialist referral |
Frequently Asked Questions
What is eGFR?
Estimated glomerular filtration rate (eGFR) measures how efficiently your kidneys filter waste from blood. Values above 90 mL/min/1.73m² are considered normal, though slight reductions with age are expected. eGFR below 60 for three months or longer indicates chronic kidney disease.
Why doesn’t this calculator include ethnicity?
NICE removed ethnicity adjustment from UK guidelines in 2021. Previous adjustments for Black ethnicity were based on outdated assumptions and did not reflect population diversity. Current UK practice uses the same formula for all ethnic groups.
Should I use eGFR or creatinine clearance for drug dosing?
For most drugs and patients, eGFR can guide dose adjustments. However, creatinine clearance (CrCl) should be used for direct-acting oral anticoagulants (DOACs), drugs with narrow therapeutic indices that are mainly kidney-excreted, toxic drugs, elderly patients, and those with extreme muscle mass variations.
What if my eGFR has suddenly dropped?
A sudden significant decline requires repeat testing within two weeks to exclude acute kidney injury. Changes up to 10% may represent normal biological or laboratory variation. Always assess trends over time rather than relying on single readings.
Can I use this calculator for children?
No. The CKD-EPI equation is only validated for adults aged 18 and above. Paediatric patients require specific equations such as the Schwartz formula.
When should someone be referred to a nephrologist?
Referral criteria include: eGFR <30 mL/min/1.73m², ACR >70 mg/mmol in non-diabetics, sustained decrease in eGFR, ACR >30 mg/mmol with haematuria, or signs suggesting glomerular disease or systemic conditions affecting kidneys.
Risk Factors for CKD
Regular eGFR and ACR testing is recommended for individuals with the following risk factors:
- Diabetes mellitus (type 1 or type 2)
- Hypertension requiring treatment
- Previous episodes of acute kidney injury
- Cardiovascular disease (ischaemic heart disease, chronic heart failure, peripheral vascular disease, cerebrovascular disease)
- Structural renal tract disease, recurrent kidney stones, or prostatic hypertrophy
- Multi-system diseases with potential kidney involvement (e.g., systemic lupus erythematosus)
- Gout
- Family history of stage G5 CKD or hereditary kidney disease
- Incidental detection of haematuria or proteinuria
Lifestyle Modifications
For patients with early-stage CKD or those at risk, lifestyle changes can slow progression:
- Achieve and maintain healthy blood pressure (target <130/80 mmHg if ACR >70 mg/mmol)
- Control blood glucose levels if diabetic (HbA1c target typically 48-53 mmol/mol)
- Maintain healthy weight and regular physical activity
- Reduce sodium intake to <6g daily
- Avoid nephrotoxic medications (NSAIDs, certain antibiotics) without medical supervision
- Stop smoking
- Limit alcohol consumption
- Stay well hydrated unless fluid restriction advised
Difference Between CKD-EPI and MDRD
The CKD-EPI equation replaced the MDRD (Modification of Diet in Renal Disease) formula in UK practice due to improved accuracy:
- CKD-EPI provides more reliable estimates when eGFR is near or above normal (>60 mL/min/1.73m²)
- MDRD tended to underestimate kidney function at higher eGFR ranges
- CKD-EPI reduces misclassification of patients with normal or mildly reduced kidney function
- Both equations have limitations at extremes of body composition
- MDRD may still appear in older literature but is no longer recommended for routine use in the UK
Laboratory Considerations
Accurate eGFR calculation depends on proper sample handling and creatinine measurement:
- NICE recommends enzymatic creatinine assays over Jaffe colorimetric methods for better specificity
- Samples should be processed within 12 hours of venepuncture
- Patients should avoid meat consumption for 12 hours before testing
- Standardised creatinine measurement (IDMS-traceable) is essential for accurate results
- Different laboratories may report slightly different values due to assay variations
References
National Institute for Health and Care Excellence. (2021). Chronic kidney disease: assessment and management. NICE guideline [NG203]. Available at: www.nice.org.uk/guidance/ng203
UK Kidney Association. (2024). Measurement of kidney function. UK eCKD Guide. Available at: www.ukkidney.org/health-professionals/information-resources/uk-eckd-guide
Levey AS, Stevens LA, Schmid CH, et al. (2009). A new equation to estimate glomerular filtration rate. Annals of Internal Medicine, 150(9):604-612.
Kidney Disease: Improving Global Outcomes (KDIGO). (2024). KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney International, 105(4S):S117-S314.
Delgado C, Baweja M, Crews DC, et al. (2022). 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, 79(2):268-288.