Dehydration is a common problem in patients undergoing hip fracture surgery. Sonographic inferior vena cava (IVC) diameter measurement evaluates to estimate volume status. The aim of the study to evaluate the relationship between IVC measurements (expiratory diameter of IVC, collabsibility index [CI], inspiratory diameter of IVC) and blood urea nitrogen (BUN)/creatinine ratio in patients undergoing hip fracture surgery. Ultrasonography of IVC was performed on 35 patients underwent hip fracture surgery. The end-expiratory diameter of IVC, end-inspiratory diameter of IVC, and CI were assessed preoperatively. The patients were classified as group 1 for BUN/Cr ratio <20, group 2 for BUN/Cr ratio of >20. Sonographic IVC measurement was not successful in 14.2% of patients and 30 patients remained. The mean age was 80.43 ± 11.10 (58-95) years. The IVC diameter values had no discriminatory value for the prediction of dehydration according to BUN/creatinine ratio (P > .05). Receiver operating characteristic curve indicated that area under the curve (AUC) for CI: 49.5%, (95% CI 26.5-72.5) P > .05; for IVC inspiratory diameter: AUC: 43.3%, (95% CI, 19.9-66.6) P > .05; for IVC expiratory diameter: AUC: 45.5%, (95% CI, 26.6-65.4) P > .05. No correlations of BUN/creatinine ratio with CI and IVC expiratory diameter were found (as r = -0.262 [P = .163]; [r = 0.206, P = .274]; respectively). There were not any correlation in linear regression analysis model between BUN/Cr ratio according to independent variables (Age, CI, IVCmax, IVCmin) (P = .108, P = .419, P = .282, P = .257; respectively). No discriminatory relationship was found between the bedside ultrasonographic measurement of IVC parameters and BUN/creatinine ratio in patients underwent hip fracture surgery to predict the preoperative dehydration.