It's not possible for a tampon to get lost inside you. It'll stay in your vagina after you have inserted it.
The only other opening is through your cervix at the top of your vagina. But this is too small for a tampon to pass through.
Tampons have a string at 1 end that usually stays outside your body. You can remove the tampon at any time using the string.
It's possible for the string to end up inside your body. This can happen if you already have a tampon in and you insert another one, or you have sex with a tampon in.
But even if the string is inside you, you'll usually be able to feel the tampon and pull it out.
If a tampon gets stuck inside you and you can't get it out, go to your GP practice or nearest sexual health clinic. Healthcare staff will be able to remove it for you.
If you can't get to your GP or a sexual health clinic, call NHS 111 for advice.
Tampon manufacturers advise that a tampon shouldn't be left in for more than 8 hours.