PURPOSE: This study aimed at comparing the costs of spinal fusion surgery between patients with and without diabetes. METHODS: Following PRISMA guidelines, a systematic search of four databases was conducted. A meta-analysis was performed on comparative studies examining diabetic versus non-diabetic adults undergoing cervical/lumbar fusion in terms of cost. Heterogeneity was assessed using the I2 test. Standardized mean differences (SMD) and odds ratios (OR) with 95% confidence intervals (CI) were calculated using a random-effects model in the presence of heterogeneity. RESULTS: Twenty-two studies were included in this meta-analysis. Standardized costs were significantly higher in the diabetic group (SMD 0.02, 95% CI 0.01 to 0.03, p <
0.05). The excess cost per diabetic patient undergoing spinal fusion surgery was estimated to be ,492 (95% CI: ,620 to ,363). The length of stay (LOS) was significantly longer in the diabetes group (MD 0.42, 95% CI 0.24 to 0.60, p <
0.001). No significant difference was observed in intensive care unit admission between the groups (OR 4.15, 95% CI 0.55 to 31.40, p >
0.05). Reoperation showed no significant differences between the groups (OR 1.14, 95% CI 0.96 to 1.35, p >
0.05). However, 30-day and 90-day readmissions were significantly higher in the diabetes group: (OR 1.42, 95% CI 1.24 to 1.62, p <
0.05) and (OR 1.39, 95% CI 1.15 to 1.68, p <
0.001), respectively. Non-routine or non-home discharge was also significantly higher in the diabetes group (OR 1.89, 95% CI 1.67 to 2.13, p <
0.001). CONCLUSION: Patients with diabetes undergoing spinal fusion surgery had increased costs, prolonged LOS, increased 30-day/90-day readmission rates, and more frequent non-routine discharges.