It is normal to have a strong menstrual blood odor, especially in the middle of the menstrual period because of the relatively large amount of bleeding, so it is normal to have a large blood odor, in the period of menstrual volume is relatively small blood odor. The main components of menstrual blood include water, broken endometrium, red blood cells, white blood cells, platelets, fibrinogen and so on. Among them, red blood cells contain divalent iron ions, so they cause the menstrual blood to have a fishy smell. Diseases that can cause increased menstrual bleeding in pathological conditions can also aggravate the hemorrhagic odor of menstruation such as submucosal fibroids, endometrial polyps, and functional uterine bleeding. If you have malignant endometrial lesions, in addition to a fishy smell, you may have a fishy smell that indicates an abnormality, and you need to go to the hospital promptly.