A woman who experiences less blood on the first day of her period is a normal physiological phenomenon if her menstrual cycle is relatively regular in her daily life. Because menstrual blood is formed by the shedding of the endometrium, less endometrium is shed on the first day of menstruation therefore less bleeding. Especially on the first day of menstruation or two days after the end of menstruation, if there are no other uncomfortable symptoms during the whole menstrual period, the amount of menstrual blood is normal without too much worry. In case of low blood volume during menstruation, it is necessary to go to the hospital for examination. When women have low estrogen or adhesions in the endometrium, as well as polycystic ovary syndrome can cause low menstrual blood volume. It is recommended that women pay attention to keeping warm in life to avoid causing uterine cold, which can also lead to low menstrual blood flow, and pay attention to vaginal care in daily life.