Severe diabetic macular edema (DME) is often resistant to anti-vascular endothelial growth factor therapy. Steroids are particularly effective at reducing edema by suppressing inflammation; they are also used as an alternative to expensive anti-vascular endothelial growth factor therapy in some patients. Therefore, the use of steroids in DME reflects an unmet need for anti-vascular endothelial growth factor therapy. Notably, triamcinolone acetonide (TA) injections are widely used in Japan. Here, we evaluated the frequency of TA as an indicator of the efficacy of sodium-glucose cotransporter 2 inhibitors (SGLT2is) in DME treatment using a health insurance claims database. In this cohort study, we retrospectively analyzed the health insurance claims data of 11 million Japanese individuals from 2005 to 2019. The frequency and duration of TA injection after the initiation of SGLT2is or other antidiabetic drugs were analyzed. Among the 2,412 matched patients with DME, the incidence rate of TA injection was 63.8 times per 1,000 person-years in SGLT2i users and 94.9 times per 1,000 person-years in non-users. SGLT2is reduced the risk for the first (P = 0.0024, hazard ratio 0.66, 95% confidence interval 0.50-0.87), second (P = 0.0019, hazard ratio 0.53, 95% confidence interval 0.35-0.80) and third TA (P = 0.0053, hazard ratio 0.44, 95% confidence interval 0.25-0.80) injections. A subanalysis of each baseline characteristic of the patients showed that SGLT2is were effective regardless of the background factors. The use of SGLT2is reduced the frequency of TA injection in patients with DME. Therefore, SGLT2i therapy might be a novel, noninvasive and low-cost adjunctive therapy for DME.