Data Collection - Age, gender, skin color, time since starting dialysis therapy and co-morbidity are recorded at baseline. Each patient's hemoglobin level, hematocrit, blood pressure, body mass index (kg/m2) are noted at the beginning and end of the study period. Serum concentration of urea, creatinine, potassium and phosphate are obtained before, after, and 30 minutes after each HD session. The dialysate concentration of urea, creatinine, potassium and phosphate and Kt/V estimated by OCM were obtained during each HD session. The laboratory analyses are conducted by a technician blinded to allocation groups. The OCM measures the difference in conductivity between the dialysate that is coming in and out of the dialyzer and gives an estimated value of Kt/V.