Abstract: BACKGROUND: Apheresis procedures use citrate as an anticoagulant to ensure the fluidity of extracorporeal blood. Citrate-related toxicities are common adverse effects in peripheral blood stem cell (PBSC) collections as they are lengthy procedures resulting in prolonged citrate exposure. Intravenous (IV) calcium administration during therapeutic apheresis procedures is commonly used to reduce the citrate-related toxicity in adults and pediatric population. Very few literature on the use of oral calcium for the prevention of citrate toxicity during PBSC collection are present. OBJECTIVE: The objective of this study was to evaluate the effect of prophylactic oral calcium in reducing citrate-related toxicities during PBSC collections. MATERIALS AND METHODS: A prospective cross-sectional study was carried out at a tertiary care hospital of Southern India. All participants received calcium carbonate – 1 g before and at each 100 ml of collection. Preprocedure, interim, and postprocedure serum calcium were measured. All procedures were done using Spectra Optia. The ACD (acid-citrate-dextrose) rate were between 1:8 to 1:14 and were adjusted for inlet draw rate. The total blood volume processed between 2.5 to 3 based on body weight. Reduction in calcium levels and adverse reactions due to hypocalcemia were observed. Data were analyzed using SPSS 23 software. RESULTS: The majority of the procedures were undisturbed and tolerable to oral calcium. A total of 97.3% of the study subjects did not experience any symptoms of hypocalcemia. Only 2.7% (One autologous and one allogenic donor) had symptoms attributable to hypocalcemia though they had preprocedure calcium >9 mg/dl. Pre- and postprocedure calcium were compared using a paired t-test which was statistically significant. CONCLUSION: Prophylactic oral calcium in PBSC collection is an effective and easy way to the prevention of citrate-related adverse effects without affecting technical performance and product efficacy.