eGFR Creatinine-Cystatin C Cal

This test estimates how well your kidneys are filtering waste from your blood by combining two different markers—creatinine and cystatin C—for a more accurate result. A higher number means your kidneys are filtering well, while a lower number may suggest your kidneys are not working as efficiently as expected. Because it uses two markers instead of one, this combined estimate is less affected by factors like muscle size or diet that can sometimes make single-marker tests misleading. Your doctor uses this value along with other information to monitor kidney health over time.

When elevated: A higher combined eGFR indicates better preserved kidney filtration function and is generally reassuring. Values consistently ≥60 mL/min/1.73 m² in the absence of other kidney damage markers suggest normal to mildly reduced kidney function. When low: A lower combined eGFR indicates reduced kidney filtration capacity and may reflect acute kidney injury, chronic kidney disease, or both. Persistent values below 60 mL/min/1.73 m² for ≥3 months are consistent with CKD, and values below 15 mL/min/1.73 m² indicate kidney failure requiring evaluation for renal replacement therapy.

eGFR is not an athlete-specific performance marker, but kidney function matters for endurance athletes and those using supplements or high-protein diets. Intense training and dehydration can temporarily affect creatinine levels, so the dual-marker approach (creatinine + cystatin C) gives a more accurate picture of actual kidney health independent of muscle mass or training volume.