Originating from south India, Siddha is a form of medicine that is said to have been given to the Siddhars (yogic masters) by gods. Of 18 Siddhars mentioned in Indian history, Agasthiyar is said to have been the one chiefly responsible for establishing the philosophies of Siddha medicine.

Siddha is an approach to medicine that incorporates a strong spiritual element, proposing that the health of the body and the soul are inextricably linked and the decline of one will ultimately lead to the decline of the other. Treatment therefore is intended to heal both entities and can only be administered by knowledgeable Siddha physicians.

Siddha medicine shares some beliefs held by Ayurvedic medicine, citing the existence of three humors: vata, pitta and kapha. These humors are required to be balanced in order for an individual to achieve good health.

Diagnosis is made by an examination that concentrates on eight aspects of the patient's body: the general appearance, the tongue, the voice, the eyes, the skin, the pulse, urine and stool. The voice is judged on its pitch while all other aspects are judged by their color.

Following diagnosis, a Siddha physician will prescribe herbs for the patient, choosing them on the basis of their abilities to balance the doshas (vata, pitta and kapha). Herbs are classified by means of five propertiea: suvai (taste), veerya (potency), guna (character), pirivu (class) and mahimai (action). They are further categorized according to their source, with those of herbal origin known as thavaram, those of inorganic origin known as thathu and those of animal origin known as jangamam.

The efficacy of Siddha medicine has not been proven by any scientific methods and is hence largely dismissed by the conventional medical community. Some consider it to be a dying industry and Siddha clinics are rarely found in the west.

Many individuals seek Siddha medicine when conventional medicine has failed to address their complaint. Siddha treatment is typically sought in India by an authentic and experienced Siddha practitioner.