If you use a sanitary napkin, remember to dispose it neatly and to change to fresh ones every 2-5 hours. Do not leave a pad on for more than 5 hours, as it may result in Bacteria build-up. If you use a tampon, change it ones every 4 to 8 hours depending upon your menstrual flow. Leaving a tampon in your body for more than 8 hours can result in toxic shock and can also become fatal. Lastly, if you use a menstrual cup, it is best to empty and re-insert the cup once every 8 hours. If your flow is light, then you may leave it for up to 12 hours, but not more than that.