I these a few months every time menses the first day menses blood color is black. What reason is thi

The color of menstrual blood on the first day of consecutive months is considered to be caused by endocrine disorders or gynecological inflammation. It may also be caused by cold in the body and retention of menstrual blood in the body for too long. It is recommended that women do a good job of keeping warm. If necessary, oral Chinese medicine for activating blood circulation and removing blood stasis can be used for conditioning.