- Either serum creatinine >150 μmol/L (>1.7 mg/dL), or creatinine clearance <50 mL/min calculated by the Cockroft Gault method, eventually confirmed by measured creatinine clearance (or measured glomerular filtration rate (GFR) using plasma clearance methods, not gamma camera-based) <50 mL/min (the measured creatinine clearance / GFR is required only as confirmatory exam).