Background: Regional citrate hemodialysis anticoagulation is used when heparin is contraindicated, but most protocols require large infusions of calcium and frequent intradialytic plasma ionized calcium measurements. Objectives: The objective of this study was to determine the safety, efficacy, and effect on calcium balance of regional citrate anticoagulation using sparse plasma ionized calcium sampling. Design: The design of this study was observational. Setting: The setting of this study was the hospital hemodialysis center. Patients: The subjects of this study were the hospital hemodialysis patients. Measurements: Dialysate calcium concentration by atomic absorption spectroscopy and total dialysate weight were used as measurements. Methods: Regional citrate anticoagulation was introduced using zero calcium dialysate, pre-dialyzer citrate infusion, and post-dialyzer calcium infusion. Infusions were adjusted based on pre- and post-dialyzer calcium measurements obtained at least twice during a 4-h dialysis. The protocol was simplified after the first 357 sessions to dispense with post-dialyzer calcium measurements. Heparin-anticoagulated sessions were performed using acetate-acidified 1.25 mmol/L calcium or citrate-acidified 1.5 mmol/L calcium dialysate. Calcium balance assessment was by complete dialysate recovery. Safety and efficacy were assessed prospectively using a point-of-care database to record ionized calcium and clinical events. Groups were compared using t test, ANOVA, Wilcoxon rank sum, or Kruskal-Wallis as appropriate. Results: Seventy-five patients received regional citrate-anticoagulated dialysis over 1051 dialysis sessions. Of these, 357 dialysis sessions were performed using the original citrate anticoagulation protocol and 694 using the simplified protocol. Dialysis was effective and safe. Only 3 dialyzers clotted; 1 patient suffered symptomatic hypercalcemia and none suffered symptomatic hypocalcemia. Calcium balance was assessed in 15 regional citrate-anticoagulated dialysis sessions and 30 heparin-anticoagulated sessions. The median calcium loss was 0.8 mmol/h dialyzed in both groups ( p = 0.43), and end of treatment ionized calcium was the same in both groups (1.07 ± 0.04 mmol/L). Limitations: Our findings for calcium balance, efficacy, and safety are valid only for the protocol studied, which excluded patient with severe liver dysfunction. Conclusions: Regional citrate dialysis can be performed safely and effectively using a sparse plasma calcium sampling protocol. The calcium balance induced by this protocol is not different to that seen in standard heparin-anticoagulated dialysis, but in the absence of prospective studies, it is unknown whether this is optimal for patient care.