Alternative medicine includes practices that differ from conventional medicine. Some alternative medicine practices are homeopathy, naturopathy, chiropractic, and herbal medicine. A typical definition is "every available approach to healing that does not fall within the realm of conventional medicine".

Alternative medicine practices may be based on unconventional belief systems or philosophies; biological data and observations or biochemical principles; and some may not follow the scientific method. They may incorporate spiritual, metaphysical, or religious underpinnings, untested practices, pre-modern medical traditions, or newly developed approaches to healing. If an alternative medical approach, previously unproven according to orthodox scientific or regulatory methodologies, is subsequently shown to be safe and effective, it may then be adopted by conventional practitioners and no longer considered "alternative".

"Alternative medicine" is often categorized together with complementary medicine using the umbrella term Complementary and alternative medicine or CAM.