Background:Recently, the prevalence of cesarean section (CS) has been on the rise and the proper uterine tone is an important issue. We investigated the effects of intravenous (IV) ketamine on intraoperative bleeding and the need for oxytocin in CS under spinal anesthesia (SA).Methods:This study, took place at Alzahra hospital during 2020. Pregnant women candidate for elective CS under SA were divided into two groups of ketamine and placebo. In group K, after umbilical cord clamping, 0.25 mg/kg ketamine and in group P 2ccs normal saline was injected. Mean arterial pressure and heart rate were recorded at baseline, before and 5 minutes after cord clamping and at the end of the surgery. The drop in hemoglobin values, the administrated units of oxytocin and side effects were also recorded.Results:No significant difference was found in terms of patients’ demographic data (P ≥ 0.05). The mean units of administrated oxytocin in group K was 34.61±6.63 and in group P; 48.47±12.15, which was significantly different (P=0.0001). The drop in Hb was less in group K, however not statistically significant (P=0.094). The need for methergine was significantly higher in group P (P=0.0001). The mean HR was significantly higher in group P (P=0.027), however, no significant difference was observed regarding the MAP (P=0.064). The incidence of hallucination (4.8%) and nystagmus (21%) was significantly higher in group K (P= 0.0001), but nausea and vomiting were more significant in group P (P= 0.027).Conclusion:Prophylactic administration of low-dose ketamine in CS under S.A could significantly reduce the administrated oxytocin units and the need for additional utero-tonics and was associated with less drop in Hb values.