Menstruation refers to the regular cycle of uterine bleeding, month after month as scheduled, often unchanged, so there is a “monthly letter”, “monthly affairs”, “monthly water”, to show that menstruation has a “monthly rhythm” of cyclicity. This is why they are called “monthly letter”, “monthly affairs” and “monthly water” to indicate that menstruation has a “monthly rhythm” of cyclicity. Menstruation is the most significant physiological feature of women, and the first menstruation marks the arrival of puberty and the beginning of reproductive function. During the period of 30-35 years after menarche, menstruation usually occurs once a month, with a regular cycle. It is described in Suwen Shanggu Tianzhen Lun, “When a woman is seven years old, her kidney qi is strong, and her teeth are longer; at the age of two or seven, the heavenly capricorn arrives, the Ren vein is open, and the Taichong vein is strong, and the menstruation occurs at the right time, so there is a child.” Women’s menstruation has a lot to do with the fullness of kidney qi, only sufficient kidney qi, the woman will be about 14 years old, “Ren Chakra, Taichong Chakra,” menstruation will come on time, at this time also has the ability to procreate. “Seven seven, the Ren Vessel is weak, the Tai Chong Vessel is weak, the Heavenly Decadence is exhausted, the Earth Road is not accessible, so the shape is bad and childless”, a woman of about seven seventy-nine years of age, the gradual decline in kidney qi, the Heavenly Decadence is exhausted, the Ren Vessel is weak, the Tai Chong Vessel is weak, and the menopause is mostly at the age of 49 years old! According to Western medicine, menstruation refers to the cyclical shedding and bleeding of the endometrium caused by the cyclical changes in the secretion of estrogen and progesterone by the ovaries along with the cyclical ovulation of the ovaries. The establishment of regular menstruation is the main sign of the maturity of reproductive function.