The causes of black menstrual blood after menstruation are as follows: 1. If the menstrual blood stays in the uterine cavity or vagina for a longer period of time and is not discharged in time, it will manifest itself as black menstrual blood, which will become black menstrual blood. If the menstruation is black and the amount is low, it may also be related to cervical adhesions or cervical adhesions. Such patients usually have undergone uterine surgery before, such as abortion or scraping, which may cause damage to the endometrium, resulting in cervical adhesions or cervical adhesions, resulting in black menstrual blood. The causes of blood clots in menstruation are as follows: 1. Menstruation is caused by endometrial exfoliation, the shed endometrium and blood mixed together to form menstrual blood, if there is a larger endometrial shedding will form a blood clot, which is a normal physiological phenomenon, if the menstrual volume is normal, the menstrual cycle is also normal, there is only a small amount of blood clots, it is a normal situation; 2. If the menstrual period is prolonged, and the menstrual volume is relatively large, or more blood clots during menstruation, it should be taken seriously and may lead to anemia, which may be caused by fibroids, polyps in the endometrium, and inflammation of the endometrium; 3. Intrauterine devices, which may also cause increased menstrual flow; 4. Malignant tumors, such as endometrial cancer, may also manifest as heavy vaginal bleeding with blood clots; 5. Oral medications that activate blood circulation and remove blood stasis during menstruation may also all increase the amount of menstrual flow and the appearance of blood clots. Therefore, if you experience increased menstrual flow and blood clots, you should go to the gynecology department of the hospital for examination and diagnosis in order to provide symptomatic treatment.