Background: Multiple studies indicate that type II diabetes is associated with an increased mortality in breast cancer. However, in these studies the class of anti-diabetic therapy, remains an obvious confounding factor. Higher mortality has been reported in breast cancer patients treated with insulin than with metformin. Choosing a population of breast cancer patients with pre-diabetes, not receiving anti-diabetic therapy, could overcome such confounders. Methods: We conducted a retrospective cohort study to evaluate the relationship between elevated random blood sugar (RBS) levels and breast cancer outcomes. Only patients without a previous history of diabetes and who were not receiving any anti-diabetic therapy were included. The effect of elevated RBS on overall survival (OS), event-free survival (EFS) and time to tumor recurrence (TTR) were analyzed using Kaplan-Meier curves and log-rank test, and reanalyzed adjusting for age, race and obesity using multivariate Cox regression. Fisher’s exact test was used to compare binary proportions and Spearman rank correlations were used for ordinal category data in conjunction with correlation chi-square tests. Results: 234 patients with stage I-III breast cancer (mostly stage II, 177) were analyzed, of which 159 patients had a documented RBS level. 72 patients had elevated RBS ( > 120 mg/dL) and 87 had RBS < 120 mg/dL. We observed that patients with elevated RBS experienced significantly shorter OS (HR = 2.89; p = 0.0001), shorter EFS (HR = 2.44; p = 0.0006) and shorter TTR (HR = 2.16; p = 0.023). After adjusting for age ( < / ≥ 50), obesity and race via Cox regression, elevated RBS continued to display a high and statistically significant association with shorter OS (HR = 3.63; p < 0.0001), shorter EFS (HR = 3.20; p = 0.0002) and shorter TTR (HR = 3.52; p = 0.001). Additionally, among patients under 50 years of age, elevated RBS levels were associated with a significantly greater frequency of high grade tumors compared to RBS < 120 mg/dL(80% vs 45%; p = 0.02), suggesting that elevated RBS may have more impact in younger patients. Conclusions: High random blood sugar levels, reflective of a pre-diabetic state, are associated with shorter overall survival in breast cancer patients.