Comparison · Biomarker vs Biomarker
Creatinine vs eGFR
Creatinine is the thing that is measured; eGFR is the number the laboratory calculates from it. They appear side by side on every kidney blood test, and confusing them is the commonest reason kidney results are misread.
| Aspect | Creatinine | eGFR (estimated glomerular filtration rate) |
|---|---|---|
| What it is | A muscle waste product measured directly in blood | An estimate of filtration calculated from creatinine, age and sex (CKD-EPI equation) |
| Direction | Rises as kidney function falls | Falls as kidney function falls |
| Units | µmol/L (UK) or mg/dL (US) | mL/min/1.73 m² |
| Effect of muscle mass | Higher in muscular people, lower in frail people, for the same kidney function | Partly corrected by age and sex, but still misleading at extremes of muscle mass |
| Steady state | Valid at any time, but lags behind an acute change in filtration | Only valid when kidney function is stable; not used in acute kidney injury |
| Threshold use | Reference interval set by the laboratory | Chronic kidney disease staging thresholds (below 60 for 3 months = CKD stage G3 or worse) |
Where Creatinine fits
Detecting a change over hours to days (acute kidney injury), where the trend in the measured value matters and the estimate is invalid
Where eGFR (estimated glomerular filtration rate) fits
Staging chronic kidney disease, adjusting drug doses and comparing people of different ages and sexes
Educational content. A comparison explains what each test, marker or medicine is for and how they differ. It is educational and does not say which one a person should have; that decision belongs to the clinician who knows the person and the question.