“Medically necessary” means services or supplies provided by a health care provider that are:

1. appropriate for the symptoms and diagnosis or treatment of the enrollee’s condition, illness, disease, or injury,
2. in accordance with standards of good medical practice,
3. not primarily for the convenience of the enrollee or the enrollee’s health care provider, and
4. the most appropriate supply or level of service that can safely be provided to the enrollee.

http://www.oklegislature.gov/osStatuesTitle.aspx