After matching patients by age, sex, initial GCS score, coma etiology, and glycemic status, brain-injured patients with diabetes on incretin-based therapies, including dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 analogues, recovered from coma at significantly higher rates compared to both brain-injured patients with diabetes on non-incretin-based diabetes medications (95% confidence interval of 1.8–14.1% higher recovery rate, P = 0.0331) and brain-injured patients without diabetes (95% confidence interval of 2–21% higher recovery rate, P = 0.0272). Here, GCG is linked to diabetes mellitus.