OBJECTIVES: Thirty to sixty percent of prepared blood products are not transfused. Blood reserves for surgeries lead to many unused blood products, which increases hospital costs. The aim of this study is to identify the request and use profiles of blood products for elective surgeries in different surgical specialties, the influence of surgery time and demographic, clinical, and laboratory variables on the number of red blood cells (RBCs) used and to calculate the rate of transfused patients (RTP) and cross-matched and transfused (C/T) RBCs. METHODS: Observational and prospective studies. Sociodemographic, clinical and quantitative data on the request and use of blood products were collected. The influence of the data on the use of RBCs was examined by binary logistic regression. Chi-square, one-way ANOVA and Kruskal-Wallis tests were utilized to compare the data among the specialties. RESULTS: In total, 822 procedures were included. Most of the requested blood products were not used, even 24 hours postoperatively. Of the 2,483 RBC units, 314 were transfused, leaving 87.6% unused; however, cardiac, digestive tract, vascular, gynecologic, urologic and thoracic surgery procedures transfused 50%, 25%, 16.5%, 11%, 9.5% and 8.1% of requested RBCs, respectively. The factors that influenced the transfusions were age, time of surgery and cardiac surgeries. The RTP was >10% in 22 surgical types and <1% in 24 surgical types, and 88% of samples presented a C/T ratio >2.5. CONCLUSION: The RTP and C/T ratios can guide RBC requests in the preoperative period. Knowing the standard of use of blood products and developing protocols enables the optimization of reserves, reduction of costs and improvement of care.