Objectives: Prophylactic oral calcium supplement has been proposed in patients undergoing thyroidectomy in order to decrease incidence of postoperative hypocalcemia, and the duration of hospital stay. This study aimed to assess the effects of prophylactic oral calcium in patients undergoing total or subtotal thyroidectomy.Methods: Forty three patients who were scheduled for total and subtotal thyroidectomy, were randomly allocated to the case (n=23) and control (n=20) groups. Oral calcium carbonate (1 gram q 8 hours) was given to the patients in the case group starting 12 hours before surgery till 7 days post thyroidectomy. Clinical symptoms of hypocalcemia and postoperative calcium levels were compared between the two groups.Results: The mean postoperative calcium level 12 hours after surgery was not statistically different between the two groups (8.9±0.5 vs. 8.5±0.7, p=0.092); while after 24 hours, calcium level was significantly lower in the control group (8.9±0.5 vs. 8.4±0.8, p=0.037). The number of patients who had paresthesia was significantly higher in the control group than case group, at both 12 hours (p=0.02) and 24 hours postoperatively (p=0.04). Duration of hospitalization was significantly lower in the case group compared to the control group (p=0.006).Conclusions: Prophylactic oral calcium supplementation decreases the hypocalcemia related paresthesia after thyroidectomy and shortens duration of hospital stay