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This is a retrospective analysis.To test the hypothesis that there is limited utility in routinely obtaining postoperative laboratory values following minimally invasive transforaminal lumbar interbody fusion (MIS TLIF).At many institutions, it is routine to obtain a complete blood count and basic metabolic profile (BMP) following a MIS TLIF. However, the utility of this practice has not been well characterized.A total of 332 consecutive patients who underwent a primary, 1-level MIS TLIF for degenerative spinal pathology between 2007 and 2013 were identified. Patients were stratified into low-risk and high-risk cohorts based upon risk for postoperative laboratory abnormalities. Inclusion criteria for the high-risk cohort were malignancy, complicated diabetes, renal failure, liver disease, hematologic disease, or significant intraoperative blood loss (>300 mL). Preoperative and postoperative hemoglobin (Hb), hematocrit, and BMP values were compared. Any interventions that were potentially related to laboratory values were identified.Totals of 270 low-risk and 62 high-risk patients were identified. Mean postoperative Hb, hematocrit, blood urea nitrogen, sodium, potassium, and calcium values were decreased compared with preoperative values (P<0.001 for each) in both cohorts. Similar changes from preoperative levels were demonstrated in each cohort. No patients received blood product transfusion. Eleven low-risk (4.1%) and 5 high-risk patients (8.1%) received oral potassium supplementation. All patients who received potassium supplementation were asymptomatic. Most patients who were given potassium replacement consumed medications known to decrease serum potassium levels. No other interventions were performed in either group.Despite a significant decrease in mean Hb concentration following surgery, no patients required a transfusion. In total, 16 patients received potassium supplementation likely related to medication-related potassium deficits. Overall, these findings suggest that the utility of routinely obtaining a complete blood count or BMP following uncomplicated MIS TLIF may be limited except in the setting of select preoperative comorbidities and/or perioperative risk factors or events.Level III.