Methods: Patients aged ≥18 years who underwent lumbar fusion with a postoperative drain between 2017 and 2020 were included and grouped based on hospital readmission status, last 8-hour drain output (<40 mL cutoff), or drain duration (2 days cutoff). Total output of all drains, total output of the primary drain, drain duration in days, drain output per day, last 8-hour output, penultimate 8-hour output, and last 8-hour delta (last 8-hour output subtracted by penultimate 8-hour output) were collected. Continuous and categorical data were compared between groups. Multivariate logistic regression analysis and receiver operating characteristic (ROC) analysis were performed to determine whether drain variables can predict hospital readmission, postoperative blood transfusions, and postoperative anemia. Alpha was 0.05. Results: Our cohort consisted of 1,166 patients with 111 (9.5%) hospital readmissions. Results of regression analysis did not identify any of the drain variables as independent predictors of hospital readmission, postoperative blood transfusion, or postoperative anemia. ROC analysis demonstrated the drain variables to be poor predictors of hospital readmission, with the highest area under curve of 0.524 (drain duration), corresponding to a sensitivity of 61.3% and specificity of 49.9%. Conclusions Drain output or duration did not affect readmission rates following lumbar spine surgery.