This data show, for the first time, that mirtazapine has beneficial effects against diabetes-induced hyperglycemia, and that suppressive effect of this drug on GLUT2 and leptin, and upregulation effect on galanin levels, which are altered in diabetic rats, may be some of the pharmacological mechanisms underlying the exhibited anti-hyperglycemic effect of mirtazapine. This evidence concerns the gene LEP and diabetes mellitus.