The menstrual cycle is usually counted from the time when menstruation first begins, and a menstrual cycle of between 21 and 35 days is normal.
Under normal circumstances, a woman’s average menstrual cycle is about 28 days, that is, counting from the time of the onset of menstruation, and menstruation may occur 28 days later. Due to individual differences, the menstrual cycle varies somewhat, and it is normal for menstruation to be about 7 days early or late, so the menstrual cycle usually lasts between 21 and 35 days.
Menstrual cycles of less than 21 days or more than 35 days are abnormal and may be related to a variety of factors, such as polycystic ovary syndrome and pituitary tumors, which affect hormone levels in the body and may lead to an unstable menstrual cycle, and in severe cases, may also affect a woman’s fertility.
Therefore, when a woman discovers that her menstrual cycle is not normal, she should seek medical attention for examination and treatment as soon as possible to avoid adverse effects.