There is no clinical rule on how often sanitary napkins need to be changed, depending on the amount of menstrual flow. For women with heavy periods and blood clots, you can change the sanitary napkin once in two to three hours to avoid the growth of bacteria. Next, if you feel uncomfortable, you can change the sanitary napkin at any time, and it is relatively cleaner to change the sanitary napkin regularly. At the same time, try to avoid changing the sanitary napkin after the menstruation is completely soaked through, because at the beginning of the menstruation the immunity of the body is reduced because of blood loss, which is more likely to lead to pathogenic infections. Therefore, during menstruation, if possible, try to change sanitary napkins as often as possible, to keep the local vulva tissue clean and dry, to avoid pathogenic infections, which can reduce the inflammation of the reproductive tract, and for women with low menstrual flow can reduce the number of times to change sanitary napkins. In addition, it should be noted that women should also do a good job of cleanliness and hygiene during menstruation, wash the vulva, avoid strenuous exercise during menstruation, and avoid eating cold, greasy and stimulating food.