Abstract: Objective:To analyze the clinical characteristics of breast cancer patients who had hyperglycemia reactions due to che-motherapy and evaluate the significance of monitoring glucose. Methods:A total of 229 patients who had hyperglycemia during their chemotherapy sessions were included in the investigation. In particular, the participants of this study were selected based on the follow -ing criteria: those who did not have any diabetes-related diagnoses before the study period and those who had complete clinical data. At the onset of the study, the patients were divided into two groups based on the level of their blood glucose during chemotherapy (< 7mmol/L group and ≥ 7 mmol/L group). Subsequently, the patients were further divided into the following three groups based on the blood glucose level: normal, impaired glucose tolerance, and diabetes groups. The normal glucose group had 130 patients. Meanwhile, 61and 38patients belonged to the impaired glucose tolerance and diabetes groups, respectively. A total of 165 patients treated with hor -mone therapy were further distributed into tamoxifen (TAM) - (76patients) and arimedex (AI) - ( 89patients) treated groups. Results: No significant association was observed between the patients' level of blood glucose during the chemotherapy period and their clinical characteristics, including age, body mass index, histology grade, tumor characteristics, and neoadjuvant chemotherapy. A total of 15patients died during the study period. In particular, 1 (6.7%),5 (33.3%), and9 patients ( 60.0%) who belonged to the normal glucose, im-paired glucose tolerance, and diabetes groups, respectively, died with a significant difference ofP<0.01. We determined that hormone therapy was not significantly associated with the patients' succeeding blood glucose levels (P=0.79). After further classification, 52and 40patients in the TAM- and AI-treated groups had normal level of blood glucose, with a significant difference of P=0.04. Conclusion: The patients' blood glucose level during chemotherapy influenced their glucose level in the succeeding period. Hyperglycemia may eventually predict poor prognosis. This study suggests that extensive blood glucose screening and prevention strategies among breast cancer patients may be warranted.