GFR Calculator · Practical guide
CKD-EPI vs MDRD: Which eGFR Equation?
Both equations estimate kidney function from creatinine — CKD-EPI 2021 is the current preferred standard.
At a glance
The Short Answer
CKD-EPI 2021 is the equation most guidelines now prefer, especially for eGFR values above 60, where the older MDRD formula tends to underestimate kidney function. The calculator above shows both results side by side so you can compare them directly.
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Enter your own values, then compare the result with the examples below.
Results
How the Two Equations Differ
Both estimate eGFR from serum creatinine, age, and gender, but with different coefficients. MDRD (the simplified 4-variable version) uses the form 175 × creatinine^-1.154 × age^-0.203, multiplied by 0.742 for women. CKD-EPI 2021 uses separate breakpoints for low and high creatinine, which makes it more accurate in the normal range.
Side-by-Side Example
For a 60-year-old woman with a creatinine of 1.5 mg/dL:
| Equation | eGFR | CKD Stage |
|---|---|---|
| CKD-EPI 2021 | 37.6 | G3b |
| MDRD | 35.4 | G3b |
The two usually agree within a few points in the stage 3 range. The gap widens at higher eGFR values, where MDRD reads low.
Why the 2021 Update Matters
Earlier equations included a race coefficient. The CKD-EPI 2021 revision removed race from the calculation, producing a single equation for all patients. That change, plus better accuracy near normal kidney function, is why major labs have switched to CKD-EPI 2021 as their default reporting equation.
Frequently Asked Questions
Which equation do most US labs report?
Most US laboratories now report eGFR using the CKD-EPI 2021 creatinine equation, following recommendations from the National Kidney Foundation and the American Society of Nephrology.
Why did the equations remove the race variable?
Race is a social construct, not a biological one, and including it could misclassify kidney function. The 2021 CKD-EPI equation was refit without race and performs well across populations.
Do these equations work for children?
No. CKD-EPI and MDRD are validated for adults. Pediatric kidney function uses different formulas, such as the bedside Schwartz equation based on height.
Is eGFR accurate if I am very muscular or very frail?
Creatinine-based equations can mislead at extremes of muscle mass. In those cases, doctors may order a cystatin C test or a measured creatinine clearance for a better estimate.