According to The National Center for Complementary and Alternative Medicine (NCCAM), the distinction is that complementary medicine is used together with conventional medicine and alternative medicine is used in place of it:
- "Complementary medicine is used together with conventional medicine. An example of a complementary therapy is using aromatherapy to help lessen a patient's discomfort following surgery".
- "Alternative medicine is used in place of conventional medicine. An example of an alternative therapy is using a special diet to treat cancer instead of undergoing surgery, radiation, or chemotherapy that has been recommended by a conventional doctor".
Alternative medicine is the favored term among the public and many practitioners. It is really researchers who prefer the term "complementary and alternative medicine", which they call "CAM". For them, CAM usually refers to the alternative practices that have some scientific evidence showing their safety and/or effectiveness.
National Center for Complementary and Alternative Medicine. "What is complementary and alternative medicine?" 2002 NCCAM 3 August 2006 <http://nccam.nih.gov/health/whatiscam/>.