The textbook definition of menstrual flow is less than 20ml, which may be abstract, if you take a sanitary napkin, a night sanitary napkin soaked in blood when the blood volume is about 20-30ml, so if it does not reach this standard, but only slightly less than the usual menstrual flow is not a disease, no need to worry. Menstruation is not something dirty in the body, but blood coming out of the blood vessels after the normal endometrium is peeled off, so even if it is slightly less, it will not cause any harm to the body. Similar to excessive menstruation, menorrhagia is also a matter of differentiating whether there is an organic cause or not. The so-called organic problem usually refers to the reduction of menstruation due to damage to the endometrium, the part that produces menstrual blood, and the common causes include post-abortion cavity adhesions, endometrial tuberculosis or low menstrual flow secondary to the reduction of endometrial volume after uterine surgery. This is also known clinically as Asherman’s syndrome and is usually caused by damage to the basal lining of the endometrium during the abortion. Uterine adhesions can be identified by ultrasound, hysterosalpingography or hysteroscopy, and can also be treated by hysteroscopic surgery. Endometrial tuberculosis destroys the functional layer of the endometrium, causing a low menstrual flow. Such problems, which are usually irreversible, make the treatment of infertility due to endometrial tuberculosis difficult. The oral contraceptive pill, or the use of hormonal contraceptive rings, can also cause menorrhagia, which is related to the decrease in estrogen. In addition to organic problems, low menstrual flow is usually related to the function of the ovaries. During adolescence or perimenopause, low menstrual flow can occur due to imperfection of the pituitary-ovarian function axis or decline of ovarian function (see Mechanism of Menstruation 002). Abnormalities in other endocrine organs in the body, such as hypothyroidism, increased prolactin, high insulin levels or high androgen levels, may also cause abnormalities in the pituitary-ovarian function axis and lead to decreased menstrual flow. Decreased fat content in the body due to excessive exercise and weight loss is also a cause of decreased menstrual flow or even amenorrhea. In addition to the above mentioned problems, most women have reduced menstrual flow due to mental and emotional problems, such as exam stress or emotional stress in anticipation of something happening, which inhibits the secretion of hormones in the pituitary gland of the hypothalamus and subsequently leads to a decrease in ovarian estrogen secretion, which also leads to reduced menstrual flow. For functional reduced menstrual flow, the first thing to do is to find the cause. If the problem is related to other functional axes in the body, you need to treat the other causes accordingly, such as thyroid hormone supplementation in case of low thyroid. If the problem is related to mental or emotional factors, it is usually possible to return to normal after the external factors are removed. The incidence of infertility in women with low menstrual flow does not differ from that of women with normal menstrual flow, so no special treatment is usually necessary.