All tampon users know that you're supposed to change your tampon periodically, which, according to tampon manufacturers, is every eight hours. But sometimes, life gets in the way of your changes: You're wearing a jumpsuit and don't feel like going to the bathroom; you're stuck on a long car ride and don't want to stop; or you're just feeling lazy and forget to go to the bathroom while binge-watching Terrace House for 10 hours straight. Even though you may be able to pull off wearing the same tampon for more than the allotted time, that doesn't mean it's a good idea.

Normally, your vagina contains a certain amount of bacteria, which helps it stay balanced and happy. But if the bacteria suddenly gets more nutrients and grows too much, or if it starts growing in places it doesn't belong, then the otherwise healthy bacteria can become dangerous. And, as it turns out, "a blood-soaked tampon that lingers for a long time is like a petri dish for bacteria," says Katharine O'Connell White, MD, MPH, director, Fellowship in Family Planning, department of Ob/Gyn at Boston University, Boston Medical Center. "All of the sudden, bacteria that wouldn't hurt you on most days has a thriving environment to grow," she says.

When there's an overgrowth of bacteria in your vagina, then it can lead to a vaginal infection, like bacterial vaginosis, Dr. White says. Bacterial vaginosis is not ideal, because it can lead to uncomfortable symptoms like itching, discharge, and odor — but it is treatable. In very rare cases, if the type of bacteria called Staphylococcus grows, then it can release toxins that cause toxic shock syndrome, she says. "The risk of toxic shock syndrome is not high, but it is real," she says.

Ideally, you should change your tampon before the bacteria has a chance to colonize, Dr. White says. "The more frequently you change them, the fresher they are, and the less likely the bacteria will grow," she says. You should always follow the instructions that come with your tampons, which usually state that you can leave it in for four to eight hours, although Dr. White says that eight hours is really pushing it. And if you're sleeping more than eight hours, then you should just use a pad so you don't have to worry about changing it at night, she says.

If you're the type to rely on a super tampon to last you all day, that's not a great idea either. According to Dr. White, that's the "exact opposite of what you should be doing for best vaginal health." With a super tampon, there's more opportunities for bacteria to grow, because it's left inside of you longer, she says. And if you pull out a dry super tampon, then it can lead to micro-tears on the inside of your vagina. "It's a tiny cut that you wouldn't notice, but it is big enough for bacteria to get into," she says.

In general, Dr. White's advice is typically to "slenderize your tampon game," and use the smallest one that you can get away with. If your flow is light enough that you can get away with just a panty liner, do that, she says. (And definitely never use a tampon to manage vaginal discharge, which she says some people do.)

So, the bottom line to remember: "We don't want to leave anything in your vagina longer than it needs to be," Dr. White says. Even menstrual cups, which claim they can be in for up to 12 hours, shouldn't be used for more than eight hours. "Treat it like a tampon and don't leave it in very long," she says. You may need to end up taking more bathroom trips, but the good news is you can get back to doing whatever you were before you were rudely interrupted by your bleeding uterus.