Stage 1: Kidneys are damaged but still working well (eGFR 90+). Usually no symptoms, but protein in urine shows early damage.

Stage 2: Mild decrease in kidney function (eGFR 60-89). May have UTIs or slight swelling in hands/feet.

Stage 3: Moderate damage split into:
- 3a (eGFR 45-59): Fatigue, dark urine, swelling, muscle cramps start
- 3b (eGFR 30-44): Same symptoms but more severe

Stage 4: Severe damage (eGFR 15-29) with nausea, vomiting, high blood pressure, anemia.

Stage 5: Kidney failure (eGFR <15) requiring dialysis or transplant. Very serious symptoms need immediate treatment.