This study investigated the relation between hemolytic anemia and the water disinfection schedule of hospitals. Ten dialysis centres in Riyadh, Saudi Arabia, were selected, with a total of 1000 patients undergoing extended hemodialysis/hemodiafiltration (HD/HF). Hemoglobin (Hb) concentration analyses were performed during one year period in 2015. Hb concentrations were compared on days when the water supply was disinfected using chloramines, with data measured on disinfection-free days. Of those patients 650 were males and 350 were females. Their mean ages were 46.74 ± 13.50 years. The results revealed a maximum Hb level of 15.98 g/dL during HD/HF on the disinfection-free days. The Hb level decreased to 9.32 g/dL with maximum value of 11.57 g/dL on the days of water disinfection (p < 0.001 compared to disinfection-free days). This study revealed the need for developing effective, less hazardous, less expensive and more suitable alternatives to sterilize dialysis water to ensure the quality of health services provided.