Low menstrual flow with blood clots and a dark color may be caused by a decline or diminished ovarian function, or by uterine adhesions or uterine scarring. Endocrine disorders such as abnormal thyroid function, high prolactin or polycystic ovary syndrome may also affect menstrual flow. Oral medication that affects menstruation, such as antidepressants or diet pills, may also cause this symptom. If you have recently suffered from frequent insomnia or stayed up late or were stressed out, it may affect ovulation and affect the amount of menstruation. Therefore, it is best to come to the hospital on the third day of your period on an empty stomach to have a blood test for endocrine tests to rule out ovarian decline. In addition, after a clear diagnosis, menstruation should be regulated under the guidance of the doctor. If there are uterine adhesions, hysteroscopic electrodesis of uterine adhesions may be required and the endometrium should be replenished with estrogen in order to restore menstrual flow.