Acupuncture is a collection of procedures involving penetration of the skin with needles to stimulate certain points on the body. In its classical form it is a characteristic component of traditional Chinese medicine (TCM). It has been categorized as a complementary health approach.^[1] According to traditional Chinese medicine, stimulating specific acupuncture points corrects imbalances in the flow of qi through channels known as meridians.^[2] Scientific investigation has not found any histological or physiological correlates for traditional Chinese concepts such as qi, meridians, and acupuncture points,^[3][4][5] and some contemporary practitioners use acupuncture without following the traditional Chinese approach.^[6][7]

Although minimally invasive, the puncturing of the skin with acupuncture needles poses problems when designing trials that adequately controls for placebo effects.^[8][9][10] A number of studies comparing traditional acupuncture to sham procedures found that both sham and traditional acupuncture were superior to usual care but were themselves equivalent; findings apparently at odds with traditional Chinese theories regarding acupuncture point specificity.^[11] The evidence does not rule out the possibility that the effects of acupuncture may be entirely due to placebo.^[12][13][14]

Acupuncture's use for certain conditions has been endorsed by the United States National Institutes of Health, the National Health Service of the United Kingdom, the World Health Organization,[2][15] and the National Center for Complementary and Alternative Medicine.[16][17][18][19] Some scientists have criticized these endorsements as being unduly credulous and not including objections to or criticisms of the research used to support acupuncture's effectiveness.[20][21][22] There is general agreement that acupuncture is relatively safe[23] when administered by qualified practitioners using sterile needles[16][24][25][26] and carries a very low risk of serious adverse effects.[27]