Complementary medicine is any treatment that is outside the traditional medicine or practice of a person's primary health system. A treatment that is complementary in one culture may be traditional in another; for example, acupuncture, although traditional in China, is considered alternative or complementary in the United States.

A central concept of many types of complementary medicine is to give thought and care to the whole person (holistic) rather than providing treatment for a specific disease or symptom. This holistic view and the emphasis on maintaining good health may be appealing for those with chronic illness or for those who want to improve their quality of life through lifestyle changes.

The use of complementary medicine in the U.S. is on the rise. People often seek out complementary therapies for long-term (chronic) conditions that have not been successfully treated with conventional medicine as well as to maintain and improve wellness and quality of life.