Menstrual blood is non-clotting and is also dark red in color. Normally, although menstrual blood does not clot, some people may have very small blood clots, which is a normal phenomenon. However, if there is a large blood clot, it is abnormal to discharge it on the first day of menstruation. Clinically, it is commonly seen in submucosal fibroids, endometrial polyps, inflammation of the endometrium, or endometrial disease, which may lead to the phenomenon of blood clots in menstrual blood. It is recommended to do the appropriate examination after the menstrual period is clean, through ultrasound, gynecological examination to understand whether there is a pelvic tumor, to understand the condition of the endometrium, and then give the appropriate clinical treatment. If necessary, diagnostic scraping is needed to understand the condition.