According to internationally recognised guidelines designated by the American Kidney Foundation, chronic kidney disease is clinically classified into 5 stages according to glomerular filtration rate (GFR).
Stage 1: characterised by normal or elevated GFR and GFR ≥90.
Stage 2: characterised by mildly reduced GFR, GFR 60-89.
Stage 3a: characterised by a mild to moderate reduction in GFR, GFR 45-59.
Stage 3b: characterised by a moderate to severe reduction in GFR, GFR 30-44.
Stage 4: characterised by a severe reduction in GFR, GFR 15-29.
Stage 5: characterised by end-stage renal disease (ESRD) with GFR <15 or dialysis.