Background: A high incidence of diabetes mellitus has been reported among patients diagnosed with lumbar degenerative spinal diseases. Although epidural steroid injections are known to increase the postprocedure blood glucose level, it has not been investigated whether a lower steroid dose can reduce blood glucose excursions and still be effective in controlling patients’ subjective pain. Objective: We compared the effects of 2 common doses of triamcinolone administered via epidural steroid injections on blood glucose levels and pain control in patients with diabetes mellitus to determine an adequate epidural steroid dose. Study Design: A prospective observational study. Methods: One hundred patients with diabetes mellitus were enrolled. They received lumbar transforaminal, lumbar interlaminar, or caudal epidural triamcinolone for radiculopathy, spinal stenosis, or failed back surgery syndrome. After the type of procedure was clinically determined, the doses of triamcinolone given were randomly chosen, either 40 mg (Group 40) or 20 mg (Group 20). The patients were asked to measure their finger stick blood glucose level twice daily (fasting and postprandial) for 3 days before the injection, on the day of the injection, for 7 days after the injection, and at 14 days after the injection. They also kept a blood glucose diary. Employment status and clinical outcome were evaluated at 8 weeks after the procedure. Results: There were significant increases in fasting blood glucose (FBG) level on postprocedure day (PPD) #1 to PPD #3 in Group 40, but on PPD #1 in Group 20. Moreover, there was a significant difference in FBG between groups on PPD #1 and PPD #2 (FBG on PPD #1: 179 [51]) mg/dL in Group 40 versus 146 [50] mg/dL in Group 20, P < 0.001]. Postprandial blood glucose (PBG) level was significantly elevated in both groups from PPD #0 to PPD #3. Notably, the increase in PBG was significantly greater in Group 40 than Group 20 on PPD #0 and #1 (PBG on PPD #0: 288 [57] mg/dL versus 242 [94] mg/dL in Groups 40 and 20, respectively, P = 0.004). The numeric rating scale for pain reported by the patients decreased for 2 weeks after treatment with no difference between groups. Employment status and clinical outcome was not different between groups. Limitations: The patients who chose to participate in this study may be a cohort of well-controlled patients with diabetes mellitus. The type of procedure performed was determined by a clinical decision and not randomized. The different routes of administration and diagnosis of failed back surgery syndrome can result in different levels of systemic absorption, thereby influencing the degree and duration of hyperglycemia. In patients with FBSS, the epidural space may be destructed by surgery and adhesive changes in epidural space could be extensive. Therefore, we thought that the absorption of epidural space in these patients would be incomplete or slow compared with those without FBSS. Conclusion: Epidural steroid injections were associated with statistically significant elevations in PBG in patients with diabetes for up to 4 days after the procedure. The higher dose of triamcinolone increased FBG and PBG greater than a lower dose did without affecting pain control, employment status, or clinical outcome. Thus, with respect to glucose and pain control, 20 mg of triamcinolone appears to be recommended rather than 40 mg in patients with diabetes. Clinical Trials registration : NCT01435707 Key words: Epidural steroid injection, low back pain, diabetes, blood glucose