Dr. Terri McFadden sees kids of all ages in her pediatric practice, from babies to the occasional college student.

However, she said, there comes a time when her patients need to move on to a doctor who treats adults. Some teen patients, feeling out of place among little kids, are eager to start the transition, but others need a nudge.

"When the staff is calling my pediatric patients 'Sir,' you probably need to transition to an adult doctor," said McFadden, who is medical director for primary care for Children's Healthcare of Atlanta at Hughes Spalding.

"You have that relationship with them, and they trust you," McFadden said. "I think it's hard for them to let go.

"It really depends on the relationship you have with the child or the family," she said.

Teens are neither little kids nor adults. It's the no-man's-land essence of adolescence.

In medical settings, that often means a choice between a waiting room where teens are surrounded by tots and cartoons, or one where people are a few decades older and there is arthritis literature.

Some kids prefer the older environment, but others would rather stay with a doctor who has known them all their lives.

"There are other teenagers who hate this setup with the crying babies," McFadden said. "They hate that when they come to the pediatrician's office, they may be sitting next to a 2-year-old and a table that looks like an elephant."

Some pediatricians' offices make the effort to be more teen-friendly by offering evening hours just for adolescents and a separate area of the waiting room, McFadden said.

However, even though pediatricians are trained to treat infants through age 21, all pediatric patients need to move on at some point.

But parents should make sure their doctor is comfortable treating adolescents before asking their teen give up the pediatrician, McFadden said.

It's an important distinction that family medicine covers all ages, while internal medicine tends to focus just on adults, she says. Some internists may take teens, while others may not accept any patients younger than 18.

"I do believe that teens pose a special problem if (doctors) are not used to taking care of them," she said.

"On the outside, they look like adults, but the truth is, they still have very much an adolescent brain," McFadden said. "They process information and make choices in whole different ways than an adult would."

Doctors need to recognize that their teen patients are "people under construction, if you will. You have to understand developmentally where they are," she said.

Fortunately, teens have a doctor option that is tailor-made for them: adolescent-medicine specialists. These doctors have special training in medical and behavioral issues that affect teens, like sexuality, mood and emotional problems, and bullying on social media.

Dr. Stephanie Addison Holt, an adolescent-medicine specialist with Children's Healthcare of Atlanta, said these doctors serve as primary-care physicians, but many teens come for more specialized care, like abnormal periods, sex and mood swings.

These doctors are good for patients who "think that they need more time, or they need someone who can understand," Addison Holt said. Her waiting room has a mobile cart full of teen-friendly books, magazines and videos.

"I try to give a little more extra time, and a little more TLC, if (teens) are going through a rough patch," she said. "The teen is the star of the show."

Regardless of what kind of doctor your teenager sees, Addison Holt and McFadden said parents should allow their kids to have private time with their doctors in the exam room to discuss delicate issues.

"Teens want an opportunity to talk to their doctors, and they want their doctors to bring up those sensitive topics, and they are waiting for it," Addison Holt said.

McFadden agreed: Older kids should be building a relationship with their physician.

"It doesn't take the place of discussions you have with parents ... but there will be times when the physician wants to talk with your child alone, and that's OK," she said.