Overview
Why GFR Matters
A patient can have a serum creatinine within the laboratory reference range and still have substantially reduced kidney function, particularly when muscle mass is low.
A patient can have a serum creatinine within the laboratory reference range and still have substantially reduced kidney function, particularly when muscle mass is low. Conversely, a creatinine rise may reflect changing production or tubular handling rather than a stable change in filtration. The clinical task is therefore not to read creatinine in isolation, but to interpret an estimated GFR in context. GFR is the kidney’s filtration rate, while eGFR is a calculated, body-surface-area-indexed estimate of that rate. It helps identify chronic kidney disease, dose medicines, follow the course of disease, and recognise a dangerous decline. It does not, by itself, establish CKD, determine the cause of kidney dysfunction, or remain reliable during rapidly evolving AKI. For an NP practising in Canada, interpret the reported eGFR alongside the creatinine trend, urine albumin-to-creatinine ratio, medication exposure, hydration status, and the patient’s baseline. Canadian laboratories generally report creatinine in µmol/L and ACR in mg/mmol; eGFR remains reported as mL/min/1.73 m². A single number is a starting point. The direction and speed of change often determine the next clinical decision.