DefinitionDysfunctional uterine bleeding (DUB) is abnormal bleeding from the vagina that is due to changes in hormone levels.Alternative NamesAnovulatory bleeding; Bleeding - dysfunctional uterine; DUB; Abnormal uterine bleeding; Menorrhagia - dysfunctional; Polymenorrhea - dysfunctional; Metrorrhagia - dysfunctionalCauses, incidence, and risk factorsThe menstrual cycle, or period, is not the same for every woman. On average, menstrual flow occurs every 28 days (most women have cycles between 24 and 34 days apart), and lasts 4 - 7 days.The menstrual cycle of young girls who are just starting to have their periods can range from 21 to 45 days or more apart. Women in their 40s will often notice their menstrual cycles occurring less often.During a normal menstrual cycle, levels of different f