The usual age of transitioning from the pediatrician to an adult doctor is 18. Sometimes though, when a teen has a lot of chronic medical conditions (for example, cystic fibrosis or congenital heart disease), transitioning can be a challenge. For this reason, some pediatric offices continue to see people up to age 24. But even healthy young adults, because they are attached to the pediatrician and see them as part of the family, can still be seen by a pediatrician if the insurance company will allow it.