The normal color of menstruation is dark red. If the menstrual blood is bright red, it is common in clinical practice for the following reasons: First, when there is a submucosal fibroid, or a larger fibroid between the muscle walls. This will relatively increase the endometrial area and affect the contraction of the uterus, which will cause the blood sinuses to open. The majority of the blood that comes out this way is bright red blood, and often accompanied by the phenomenon of blood clots. Secondly, when a large piece of endometrium is shed, the blood sinuses will also open in a large amount within a short period of time, making the menstrual blood appear bright red. This condition is commonly caused by excessive activity of the endometrium or due to inflammation of the endometrium resulting in a large amount of endometrial shedding. It is recommended that a clinical examination be done after menstruation to find out if there is endometrial inflammation and to rule out the possibility of fibroids, and treatment should be given according to the results.