Palin appeared on Monday's episode of "The Oprah Winfrey Show," saying Levi Johnston is on a road that is "not a healthy place to be."
Palin's 413-page book, "Going Rogue," will be released Tuesday and she begins a book tour Wednesday in Grand Rapids, Mich.
The new memoir doesn't contain any references to Johnston, who's sparred with his former mother-in-law-to-be.
The former Alaska governor and former Republican vice presidential candidate told Winfrey that Johnston has been busy with media tours and hasn't seen his son "for a while."
Palin also says she continues "to hope for the best and to pray for Levi."