Diabetes mellitus in men may have some impact on fertility, partly in terms of erectile dysfunction of the penis and partly in terms of decreased sperm quality. 1. Erectile dysfunction: diabetes can lead to neuropathy, vasculopathy, dysfunction of endothelial cells and smooth muscle cells in the cavernous sinus of the penis, which together lead to erectile dysfunction. 2. Decrease in sperm quality: Diabetes mellitus accompanied by neurological dysfunction and vascular lesions can lead to restriction of normal function of testes, epididymis and other tissues, which can directly or indirectly lead to a decrease in sperm quality, mainly including a decrease in the total amount of semen and a decrease in the vitality of sperms, which will lead to a decrease in male fertility. Male diabetic patients should actively control blood glucose and prevent complications under the guidance of doctors.