How do you diaper a 12 year old?

If a 12yo would need diapers and have been checked by a doctor so you know why he needs them since this is not normal for a 12 yo, there are diapers for older children and adults. There's Up&Go just like there is for small children and also normal diapers. he should be able to put them on himself but if he's bedridden you roll him to each side and put the diaper underneath and then attach it to the sides.