eGFR means estimated glomerular filtration rate. It is not a measured filtration rate. Labs estimate it from a blood creatinine (sometimes cystatin C), plus age and sex, using a published equation. The equation name belongs next to the number. Two equations on the same creatinine often disagree.
The three names you will see
- CKD-EPI: the equation most current lab reports use for adults. The 2021 version does not use a race coefficient.
- MDRD: an older estimate. You may still see it on past reports. Do not mix an old MDRD value with a new CKD-EPI value and call the change a real drop in kidney function.
- Cockcroft-Gault: estimates creatinine clearance in mL/min, not eGFR in mL/min/1.73 m². Some drug labels still cite it. It is not a substitute line on a CKD-EPI report.
How to read a result without over-reading it
Confirm the equation, the units, and whether the lab used creatinine, cystatin C, or both. Creatinine moves with muscle mass, meat meals, and some medicines, so one low eGFR is a reason to repeat and review, not a label. Staging of chronic kidney disease uses a confirmed reduction plus other findings, and that decision belongs to a clinician.
When a drug reference names Cockcroft-Gault, use that calculator with the weight the reference specifies (actual, ideal, or adjusted). When the lab prints CKD-EPI, quote CKD-EPI. Write the equation name in the note so the next person does not “convert” it by hand.