Estimated kidney function (CKD-EPI).
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(−1.200) × 0.9938^Age × (1.012 if Female)
The CKD-EPI 2021 equation (race-free version, published in the New England Journal of Medicine, 2021) calculates eGFR from serum creatinine (Scr), age, and sex. It replaced the older MDRD formula because it is more accurate across a wider range of kidney function levels.
The equation uses two sub-expressions depending on whether creatinine is below or above a sex-specific threshold (κ). The general form is:
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(−1.200) × 0.9938^Age × [1.012 if female]
where κ is 0.7 for females and 0.9 for males, and α is −0.241 for females and −0.302 for males.
Step 1 – Compute Scr/κ: 1.1 / 0.7 = 1.5714 Step 2 – min(1.5714, 1) = 1.000; max(1.5714, 1) = 1.5714 Step 3 – min term: 1.000^(−0.241) = 1.0000 Step 4 – max term: 1.5714^(−1.200) = e^(−1.200 × ln(1.5714)) = e^(−1.200 × 0.4520) = e^(−0.5424) ≈ 0.5814 Step 5 – Age factor: 0.9938^55 = e^(55 × ln(0.9938)) = e^(55 × −0.006219) = e^(−0.3420) ≈ 0.7104 Step 6 – Female factor: 1.012 Step 7 – eGFR = 142 × 1.0000 × 0.5814 × 0.7104 × 1.012 ≈ 142 × 0.5814 × 0.7104 × 1.012 ≈ 59.4
Result: eGFR ≈ 59 mL/min/1.73 m² → CKD Stage G3a (mildly to moderately decreased kidney function, range 45–59)
An eGFR of 59 mL/min/1.73 m² falls in the G3a range (45–59) according to KDIGO 2012 classification, meaning this patient has mildly to moderately decreased kidney function. This is not normal for a 55-year-old and warrants further evaluation by a physician. Values ≥ 60 with no other markers of kidney damage are generally considered within the normal-to-mildly-reduced range, while values below 15 indicate kidney failure. A single eGFR reading is a snapshot — clinicians look for persistent changes over at least 3 months before diagnosing CKD.
Glomerular Filtration Rate (GFR) is the volume of fluid filtered by the kidney glomeruli per unit time. Because directly measuring GFR requires infusing a marker substance (e.g., inulin), clinicians use estimated GFR (eGFR) derived from creatinine — a waste product of muscle metabolism that the kidneys filter at a predictable rate.
| Stage | eGFR (mL/min/1.73 m²) | Description | |-------|------------------------|-------------| | G1 | ≥ 90 | Normal or high | | G2 | 60–89 | Mildly decreased | | G3a | 45–59 | Mildly to moderately decreased | | G3b | 30–44 | Moderately to severely decreased | | G4 | 15–29 | Severely decreased | | G5 | < 15 | Kidney failure |
The original CKD-EPI 2009 equation included a race coefficient for Black individuals. In 2021, Inker et al. published a revised, race-free version in the New England Journal of Medicine after research showed the race adjustment was not biologically justified and led to inequitable care. Most major US medical centers and laboratories now use this 2021 version.
An eGFR below 60 persisting for more than 3 months, or any eGFR with signs like protein in urine (albuminuria), blood in urine, or abnormal kidney imaging, requires medical evaluation. Early CKD is largely symptom-free, making screening important for at-risk individuals (diabetes, hypertension, family history).
⚠️ Disclaimer: This calculator is intended for educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional to interpret your results.
KDIGO guidelines classify CKD into five stages (G1–G5) based on eGFR, combined with albuminuria categories (A1–A3). Stage G3 (eGFR 30–59) is particularly important as it significantly increases cardiovascular risk and requires regular monitoring. Staging guides treatment intensity and referral to nephrology.
Measured GFR (mGFR) uses clearance of an exogenous marker like iohexol or inulin and is the gold standard. It is expensive and time-consuming. eGFR from creatinine is an accurate, low-cost proxy suitable for routine screening and monitoring, though it can deviate from mGFR in edge cases like extreme muscle mass or diet.
Yes. Treating underlying causes like hypertension (with ACE inhibitors or ARBs) or diabetes can slow decline and sometimes modestly improve eGFR. Acute causes of low eGFR (dehydration, infection) often fully resolve with treatment. True chronic structural kidney damage is generally irreversible but its progression can be slowed.
Small differences (1–3 mL/min/1.73 m²) are normal due to rounding or slight variations in the creatinine assay calibration used by your lab. If the difference is larger, confirm whether your lab uses the CKD-EPI 2021 equation or an older formula (MDRD or CKD-EPI 2009), and check that you entered the correct creatinine value and units.
For adults under 40, an eGFR ≥ 90 mL/min/1.73 m² is typical. eGFR naturally declines about 1 mL/min/year after age 40, so an eGFR of 75 in a healthy 70-year-old may be expected. However, any value below 60 persisting for 3+ months is classified as CKD regardless of age.
Yes, but you must first convert: divide your µmol/L value by 88.4 to get mg/dL, then enter the converted number. For example, 97 µmol/L ÷ 88.4 ≈ 1.10 mg/dL.
They are related but not identical. Creatinine clearance (CrCl) from the Cockcroft-Gault equation estimates actual kidney clearance and is often used for drug dosing. eGFR from CKD-EPI is indexed to body surface area (1.73 m²) and is preferred for CKD staging.
Creatinine itself is not dangerous, but a very high level signals poor kidney filtration. A creatinine above 4–5 mg/dL typically corresponds to eGFR < 15 (Stage G5, kidney failure). Seek immediate medical care for rapidly rising creatinine, especially with decreased urine output.
The CKD-EPI equation does not directly account for body weight or muscle mass. Bodybuilders may have elevated creatinine and falsely low eGFR, while frail elderly individuals may have normal creatinine despite poor kidney function. Cystatin C-based or combined creatinine-cystatin C equations are more reliable in such cases.
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