Menstrual blood is menstrual blood, and the odor of menstrual blood may be related to poor personal hygiene habits, endometritis or endometrial cancer. If menstrual blood still smells bad after changing personal hygiene habits, it is recommended to consult a doctor in time to find out the cause of the odor and treat it under the doctor’s guidance. 1. Poor personal hygiene habits: If the patient does not change sanitary napkins frequently during menstruation, the menstrual blood on the sanitary napkin can easily breed bacteria in the moist environment, and the bacteria grow and multiply in the nutritious environment of the menstrual blood, which will emit a bad odor and lead to the bad smell of the menstrual blood, so the woman needs to change sanitary napkins frequently during menstruation. 2. Endometritis: endometrial inflammation due to infection of various pathogenic bacteria leads to menstrual blood odor, timely anti-infective treatment will gradually improve the bad smell, commonly used drugs are tinidazole, metronidazole and so on. 3. Endometrial cancer: patients often show increased menstrual blood, irregular bleeding, abnormal fluid discharge from vagina, etc. When endometrial cancer is in advanced stage, because of soft tissue erosion leading to malodor of menstrual blood, it is necessary to do pathology to make a clear diagnosis. There may also be other reasons, so it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or therapy.