Objective To evaluate the value of blood urea nitrogen (BUN)/creatinine (Cr) ratio for guiding the access route of double balloon enteroscopy (DBE) for small intestinal bleeding. Methods The clinical information was collected from 105 patients who underwent DBE for suspected small intestinal bleeding at Air Force Medical Center from January 2015 to October 2019. Patients were divided into the elevated BUN/Cr group (n=52) and the normal BUN/Cr group (n=53), with a cut-off value of 81. Comparison was made for the detection rate of lesions between the oral route and anal route separately in the two groups using Chi-square test. Results Among the 105 patients with suspected small intestinal bleeding, definite causes of bleeding were identified in 79 patients by DBE, and the overall lesion detection rate was 75.24% (79/105). In the elevated BUN/Cr group, the overall lesion detection rate was 76.92% (40/52), among which 79.49% (31/39) was through oral and 47.37% (9/19) through anal enteroscopy. In the normal BUN/Cr group, the overall lesion detection rate was 73.58% (39/53), and 63.64% (21/33) was transoral and 51.43% (18/35) transanal. The lesion detection rate of transoral enteroscopy in the elevated group was significantly higher than that in the normal group (χ2=6.576，P=0.010).There was no significant difference in the lesion detection rate of transanal enteroscopy between the two groups (χ2=2.230, P=0.135). Conclusion For patients with active small intestinal bleeding (active bleeding within 48 hours), the BUN/Cr ratio higher than 81 may indicate that DBE should be performed firstly via oral route.