<h3>BACKGROUND CONTEXT</h3> Spinal tumors, which are classified as tumors of the spinal cord, spinal meninges and cauda equina, are relatively rare with an overall incidence of 0.62 per 100,000 persons in the United States. While these tumors are rare, they can lead to neurological deficits. Because of these neurological complications, surgical resection is a necessity in many cases. The management and surgical intervention of spinal tumors can be complex and expensive. One of the most frequently performed components of the preoperative workup for spine surgery patients is preoperative laboratory testing, accounting for approximately 3 billion dollars in spending annually. Despite this frequent use of preoperative laboratory testing, there is minimal evidence of its impact on clinical decision-making and use in predicting postoperative complications in patients undergoing spinal tumor resection. <h3>PURPOSE</h3> The effect of baseline preoperative laboratory values on postoperative outcomes of spinal tumors remains largely unknown. This study was performed to evaluate the impact of preoperative laboratory values on surgical outcomes of spinal tumors using a large national database. <h3>STUDY DESIGN/SETTING</h3> Retrospective analysis. <h3>PATIENT SAMPLE</h3> A total of 4,662 adult spinal tumor patients (median age 59 years) were included in the analysis. <h3>METHODS</h3> We extracted the data from the American College of Surgeons (ACS) registry, National Surgical Quality Improvement Program (NSQIP), for patients undergoing surgical resection of spinal tumors from 2015 to 2019. We conducted uni- and multivariate analyses for preoperative labs on the following outcome variables: 30-day mortality, Clavien IV complications, unplanned reoperation and readmission, and nonroutine discharge destination. <h3>RESULTS</h3> Based on multivariate analysis, the most significant predictors of 30-day mortality after spine tumor surgery included hypernatremia (odds ratio, OR 5.284, 95% CI 1.152, 24.2,p 1.5 (OR 2.517, 95% CI 1.391, 4.5,p< 0.01), hypoalbuminemia (OR 2.364, 95% CI 1.910, 2.925,p< 0.001), hematocrit < 36% (OR 1.606, 95% CI 1.356, 1.903, p < 0.001), low platelet count (OR 1.597, 95% CI 1.227, 2.079, p < 0.01), leukocytosis (OR 1.594, 95% CI 1.315, 1.931, p < 0.001) and hyponatremia (OR 1.540, 95% CI 1.241, 1.912,p < 0.001). <h3>CONCLUSIONS</h3> Several preoperative labs predict poor outcomes in spinal tumor patients. The baseline laboratory values should be routinely used for preoperative risk stratification of these patients. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.