If the usual menstrual cycle is 21-35 days, with an average of 28 days, and the duration of each period is 2-8 days, with an average of 4-6 days, this is regular menstruation. If the menstrual cycle is shorter than 21 days or more than 35 days, or if each period lasts for less than two days or more than 8 days, these conditions are called irregular periods. Irregular menstruation is associated with a variety of factors, such as having fibroids, adenomyosis, endometrial polyps, luteal insufficiency, and polycystic ovary syndrome, which can lead to abnormal menstruation. When menstrual abnormalities occur, it is important to go to the hospital to identify the cause and treat it according to the cause.