No. It’s not recommended to leave a tampon in overnight or for more than 8 hours. Toxic Shock or TSS is a severe but rare condition that can occur from a bacterial infection. It occurs in about 1 in 100,000 tampon users. TSS can be caused by leaving a tampon in for a long time. This is why it’s very important that you change your tampon every few hours and not leave it in all day or overnight. Most menstrual cups can be worn for up to 12 hours. This means you can wear one all day long, or overnight before you need to empty and rinse it. Again, it’s not good to have old menstrual blood on your products for too long, so keep this in mind.