Poorly controlled diabetes has been demonstrated to correlate with worse outcomes and higher complication rates following surgery. The use of hemoglobin A1c measurements (HbA1c) as a proxy for glycemic control and as a screening tool to identify high-risk patients who would benefit from preoperative optimization has been validated in the joint replacement literature. The role of HbA1c as a predictive risk factor following spine surgery has not yet been well defined. A recent nationwide database study compared well controlled diabetics to poorly controlled diabetics (as defined by diagnosis codes) and found increased length of stay, complication rates, and costs of care postoperatively. Another study correlated perioperative HbA1c levels with postoperative infection rates following single-level decompressive lumbar spine surgery. The impact of HbA1C on postoperative complications following lumbar spinal fusion surgery has not yet been elucidated. Thus, we sought in this study to examine the relationship between perioperative glycemic control (as measured by HbA1c) and complications within 30 days following elective lumbar spinal fusion surgery. This is a retrospective cohort study comparing characteristics between patients who had a complication following lumbar spinal fusion to those who did not. We retrospectively analyzed the charts of 90 patients who underwent elective lumbar spinal fusion for complications within 30 days. Our primary outcome measure was a complication within 30 days, which included: DVT, PE, acute kidney injury (AKI), delirium, sepsis, surgical site infection, UTI, MI, reoperation, pneumonia, or anemia requiring transfusion. We retrospectively analyzed data on diabetic patients who underwent elective lumbar spinal fusions. Our study included single- as well as multilevel fusions performed either by anterior or posterior approach, as well as both instrumented and non-instrumented fusions. For each patient, an HbA1c level which had been drawn within one month of surgery was used for analysis. Our primary outcome measure was a complication within 30 days. Patient demographic and perioperative factors were compared using Pearson's chi-square test for categorical variables and an independent samples t-test for continuous variables. A receiver operating characteristic (ROC) curve was plotted to determine a threshold for HbA1c that was predictive of complications. We retrospectively analyzed the charts of 90 patients who underwent elective lumbar spinal fusion for complications within 30 days. Twelve of the 90 patients had a complication, resulting in a complication rate of 13.3%. Analysis revealed no significant difference in demographic variables including age, BMI, ethnicity, and type of diabetic medication used (p > 0.05) among patients with and without complications. The group with complications had a significantly higher mean HbA1c levels (6.82 vs 7.58, p=0.033) than those without. The ROC analysis demonstrated that the HbA1c level most predictive of postoperative complications within 30 days was 6.65 (AUC=0.721; sensitivity=83.3%; specificity=51.3%; p=0.011). Our data have demonstrated a significant relationship between perioperative HbA1c levels and the 30-day complication rate following elective spinal fusion surgery. This is consistent with prior literature which has demonstrated that poorly controlled diabetics have higher complication rates in spine surgery. Interestingly, our data determined a lower HbA1c cutoff value for predicting all complications within 30 days as compared to the previously described cutoff found to be predictive of deep infection in single level decompressions (6.65 vs 7.5). This may represent different levels of disease burden causing different complications, or may represent some other difference between the spinal fusion and single level decompression patient cohorts. This abstract does not discuss or include any applicable devices or drugs.