Alternative medicine broadly describes methods and practices used in place of, or in addition to, conventional medical treatments. The precise scope of alternative medicine is a matter of some debate and depends to a great extent on the definition of "conventional medicine."

The debate on alternative medicine is complicated further by the diversity of treatments that are categorized as "alternative." These include practices that incorporate spiritual, metaphysical, or religious underpinnings; non-European medical traditions; newly developed approaches to healing; and a number of others. Proponents of one class of alternative medicine may reject others.

Detractors from alternative medicine may also define it as "diagnosis, treatment, or therapy which can be provided legally by persons who are not licensed to diagnose and treat illness", although some medical doctor find value using alternative therapies in the practice of "complementary medicine".

Many in the scientific community define alternative medicine as any treatment, the efficacy and safety of which has not been verified through peer-reviewed, controlled studies.

The boundaries of alternative medicine have changed over time as a number of techniques and therapies once considered to be "alternative" have been accepted by mainstream medicine.