How many days does a girls menstrual cycle usually last?

A girl's menstrual period typically lasts for 2 to 7 days. A menstrual period shorter than two days is considered abnormally short, while a menstrual period longer than seven days is considered abnormally long. The normal menstrual blood volume ranges from 5 to 80 milliliters, which is approximately enough to saturate 1 to 15 sanitary pads. If the menstrual blood volume throughout the entire menstrual cycle is not enough to saturate even one sanitary pad, it is considered oligomenorrhea. Conversely, if the menstrual blood volume exceeds the capacity of 15 sanitary pads, it is considered hypermenorrhea.

The menstrual cycle typically lasts around 28 days. A menstrual cycle shorter than 21 days is considered frequent menstruation, while a cycle longer than 35 days is considered infrequent menstruation. If the difference between different menstrual cycles is greater than seven days, it is considered irregular menstruation.

Menstruation is a physiological cycle that occurs in some fertile female humans, chimpanzees, and other animals. It also occurs in certain other mammalian species, which experience an estrus cycle instead. In fertile women and female primates, the endometrium undergoes autonomous thickening, blood vessel proliferation, glandular growth and secretion, as well as periodic changes including collapse and shedding of the endometrium accompanied by bleeding, approximately once every month. This periodic vaginal bleeding or uterine bleeding is referred to as menstruation, and the blood expelled during menstruation is called menstrual blood.

Menstruation is also known by various names such as "monthly matter," "monthly water," "monthly signal," "period," "big auntie," and "seeing red." In traditional Chinese medicine, menstrual blood is referred to as "jingxue." It is called menstruation because it occurs regularly and periodically in most individuals. Strictly speaking, this bleeding should be accompanied by the maturation of ovarian follicles, ovulation, and corpus luteum formation, as well as changes in the endometrium from proliferation to secretion. However, clinically, there are instances of uterine bleeding that occur without ovulation, which is referred to as anovulatory menstruation.