If the patient usually has a normal period and suddenly has a low menstrual flow or a low menstrual flow in the recent period, consider the following possibilities: 1. Low menstrual flow due to the decline of ovarian function; the decline becomes premature ovarian failure before the age of 40, and after the age of 40, women are considered to have entered the perimenopause. 2. If the low menstrual flow occurs after an abortion or a curettage, consider the damage to the endometrium or the adhesion of the endometrium to the uterus. 3. If a woman has an intrauterine device placed in the uterine cavity, the menstrual flow may become low or even amenorrheic. 4. If a woman suffers from chronic emotional stress, mental depression, or increased work pressure, excessive dieting and other stimulating factors, it can cause a low menstrual flow. 5. If a low menstrual flow occasionally occurs, abnormal bleeding due to preterm abortion or ectopic pregnancy should be excluded. 5. Occasionally, the low menstrual flow should also be ruled out.