An overview of Cochrane reviews found that acupuncture is not effective for a wide range of conditions, and they suggest it may be effective for only chemotherapy-induced nausea/vomiting, postoperative nausea/vomiting, and idiopathic headache.
In TCM, the four diagnostic methods are: inspection, auscultation and olfaction, inquiring, and palpation.
Inspection focuses on the face and particularly on the tongue, including analysis of the tongue size, shape, tension, color and coating, and the absence or presence of teeth marks around the edge.
The most common mechanism of stimulation of acupuncture points employs penetration of the skin by thin metal needles, which are manipulated manually or the needle may be further stimulated by electrical stimulation (electroacupuncture).
Needles vary in length between 13 to 130 millimetres (0.51 to 5.12 in), with shorter needles used near the face and eyes, and longer needles in areas with thicker tissues; needle diameters vary from 0.16 mm (0.006 in) to 0.46 mm (0.018 in), with thicker needles used on more robust patients.
Thinner needles may be flexible and require tubes for insertion.
The tip of the needle should not be made too sharp to prevent breakage, although blunt needles cause more pain.
Japanese acupuncturists use extremely thin needles that are used superficially, sometimes without penetrating the skin, and surrounded by a guide tube (a 17th-century invention adopted in China and the West).
Korean acupuncture uses copper needles and has a greater focus on the hand.
The skin is sterilized and needles are inserted, frequently with a plastic guide tube.
Needles may be manipulated in various ways, including spinning, flicking, or moving up and down relative to the skin.
Since most pain is felt in the superficial layers of the skin, a quick insertion of the needle is recommended.