Normal women have monthly menstrual flow and show regular vaginal bleeding. Abnormal uterine bleeding is a very common gynecological condition in women. There are many causes of abnormal uterine bleeding, such as medication, adenomyosis, fibroids, endometrial polyps or endometritis, and functional uterine bleeding. Some women may experience abnormal bleeding if they do not take oral contraceptives according to instructions, or if they miss or stop taking them without permission, or if they take emergency contraceptives; when taking hormonal drugs to regulate menstruation, stopping them without permission can also cause abnormal uterine bleeding; adenomyosis can lead to deformation and enlargement of the uterine cavity, causing an increase in the area of the endometrium, plus adenomyoma hinders the contraction of the uterus, and the onset of menstruation can make the menstruation too long or bleeding and more than one uterine bleeding; uterine fibroids, especially when submucosal fibroids, or endometrial polyps are present, can cause irregular vaginal bleeding and even excessive menstrual flow; functional disorder uterine bleeding, which is due to endocrine disorder, resulting in abnormal uterine bleeding. In conclusion, there are many causes of abnormal uterine bleeding in women, and once it occurs, you need to go to the hospital for examination in order to clarify the cause and treat it in time.