It is not normal to have blood clots during menstruation because normal menstruation is not clotted. If there is blood clot in menstrual blood, it is often caused by the following factors: 1. uterine fibroids, especially submucosal fibroids. 2. inflammation of the endometrium. 3. polyps of the endometrium, pelvic tumors, and adenomyosis, all of which can cause blood clots in menstrual blood. Therefore, when there is blood clot in menstrual blood, it is recommended that you must go to the hospital for ultrasound examination, clotting time examination and routine blood tests after your menstrual period is clean, and then give treatment according to the results clinically.