What does the Estimated Glomerular Filtration Rate (eGFR) test measure?

Why is Estimated Glomerular Filtration Rate (eGFR) measured?

eGFR is the cornerstone of CKD diagnosis, staging, monitoring, and pharmacological dose adjustment. Within the CMP, eGFR provides the renal function result that contextualises all other panel parameters — glucose elevation in the context of reduced eGFR suggests diabetic nephropathy; hyperkalaemia with reduced eGFR indicates impaired renal potassium excretion; hyponatraemia with reduced eGFR directs a different investigation pathway than in normal renal function. eGFR below 60 mL/min/1.73m² on two occasions at least 90 days apart confirms CKD and triggers management per KDIGO guidelines including nephrology referral consideration, medication dose adjustment, and cardiovascular risk intensification.

Reference ranges

Standard reference

≥60 mL/min/1.73m² (CKD stage G1–G2 if ≥60 with kidney damage markers; CKD G3a: 45–59; G3b: 30–44; G4: 15–29; G5: <15) # REVIEWER FLAG: Confirm Quest Diagnostics eGFR equation — Quest has transitioned to the 2021 CKD-EPI creatinine equation (CKD-EPI 2021), which eliminates the race coefficient previously used in the 2009 equation. Confirm this is the current equation in use and whether Quest also reports cystatin C-based eGFR for flagged specimens. Document that values ≥60 mL/min/1.73m² are reported as '>60' by some platforms rather than as a discrete value above 60.

Functional medicine optimal

>90 mL/min/1.73m² (functional medicine optimal for full renal reserve with no subclinical impairment; values in the 60–89 range may indicate mildly decreased kidney function even without CKD diagnosis if other kidney damage markers are present). # REVIEWER FLAG: Functional optimal framing for eGFR is not standardised — reviewer to confirm.

Units

mL/min/1.73m²

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.