What we usually call a low menstrual flow is often compared to the amount of menstruation we had before. So, why does the amount of menstruation suddenly become low? What are the causes of low menstrual flow? Clinically, if the menstrual flow is less than 10ml, or if the flow is spotted, it is called low menstrual flow; if the menstrual flow is less than 5ml, it is called low menstrual flow. To be precise, low menstrual flow means that the total amount of each menstrual cycle is about 20 ml or less (that is, the amount of one night sanitary napkin wetted through). And in general, it is more normal to change 2~3 sanitary napkins per day during menstruation. Individuals can judge whether each menstrual flow is normal based on their own menstrual flow. If the amount of menstruation is significantly too little or too much than before, it is considered abnormal menstruation. So, what is the reason for a sudden low menstrual volume at one time when it was normal before? If the menstrual volume was normal in the past and only once there is a low menstrual volume, we should consider whether it is affected by a change in living habits or mental stress, etc. For example, a sudden change in the environment, excessive mental tension, or after excessive physical labor may cause a transient menstrual disorder that manifests itself as a change in menstrual volume, i.e., a decrease in menstrual volume. The low menstrual flow caused by this condition may return to normal after active adjustment and there is no need to worry too much. However, it should be noted that women of childbearing age who have sexual intercourse and suddenly experience a low menstrual flow must first consider the possibility of pregnancy, because some women may experience a small amount of vaginal bleeding in the early stages of pregnancy due to low progesterone, and must be alert to the occurrence of preterm miscarriage or ectopic pregnancy. Low (excessive) menstrual flow for more than 3 consecutive months should be taken seriously! It may be due to the following 4 reasons: 1. Endocrine disorders The most common endocrine disorders are caused by polycystic ovary syndrome, hyperandrogenemia, hyperprolactinemia, hyperthyroidism or hypothyroidism and other diseases. In addition to low menstrual flow, patients have endocrine disorders, such as polycystic ovary syndrome with obesity, hirsutism and acne; hyperprolactinemia with nipple overflow; hyperthyroidism with irritability, irritability, hot flashes and sweating and other hyper-metabolic manifestations. 2, organic lesions such as small uterine development, endometrial damage, endometrial adhesions, etc. This condition needs to be diagnosed clearly by ultrasound or hysteroscopy and other examinations. Especially if there have been several uterine operations, such as abortion, medical abortion, uterine examination, etc., it will also often lead to reduced menstrual flow. 3.Systemic disease factors Such as suffering from severe anemia, digestive system diseases, etc. resulting in malnutrition, or tumor diseases resulting in excessive consumption, etc., can cause a low menstrual volume. 4.Inappropriate living habits Frequent late nights, overwork, long-term dieting to lose weight, long-term use of birth control pills, etc., may also affect the amount of menstruation and cause low menstrual flow. In addition, eating cold food during menstruation, or wearing thin clothing that causes the abdomen to get cold, can also cause cold clotting and blood stasis, resulting in poor flow of menstrual blood, causing a decrease in menstrual volume, as well as abdominal pain, dark menstrual blood, accompanied by blood clots, etc. In conclusion, if you have a low menstrual flow once in a while, there is no need to worry too much and you need to be alert to abnormal pregnancy; however, if you have a low menstrual flow for 3 consecutive months, you must pay attention to it, go to the hospital for examination in time and choose the appropriate treatment according to the specific situation.