Menstruation with almost no blood is considered to be a decrease in menstrual flow, which is usually related to severe anemia, pregnancy-related diseases, uterine adhesions, menstrual irregularities, and so on. 1. Severe anemia: If the woman herself is severely anemic and her body’s blood supply is insufficient, the amount of menstrual flow will also be affected. 2. Pregnancy-related diseases: If you have had unprotected sex and only have this one menstrual abnormality, then it cannot be ruled out that it has something to do with pregnancy, and it may be caused by pre-eclampsia or ectopic pregnancy. 3. Uterine adhesions: If you have experienced multiple uterine operations or abortion, then the endometrium is severely damaged, causing uterine adhesions, which can also lead to decreased menstrual flow. 4. Irregular menstruation: Decrease in female hormone levels, premature ovarian failure and other factors can also lead to a decrease in menstrual flow. If there is a significant decrease in menstrual flow, it is recommended to consult a doctor in time to identify the cause and treat the symptoms.