Creatinine clearance can be divided into five stages: Stage 1, with renal damage and glomerular filtration rate (GFR) >90 ml/min. Stage 2, with renal damage accompanied by a mild decrease in GFR, GFR in the range of 60-89 ml/min. Stage 3, with a moderate decrease in GFR, GFR in the range of 30-59 ml/min. Stage 4, with a severe decrease in GFR, GFR in the range of 15-29 ml/min. Stage 5, with renal damage accompanied by a mild decrease in GFR, GFR in the range of 60-89 ml/min. Also known as the renal failure stage, the patient’s GFR is <15ml/min. Patients in this stage are in the uremic phase and it is recommended that they should undergo regular renal replacement therapy.