Oral glucosamine is a dietary supplement and is not a prescription drug in the United States.[4][5][6] Glucosamine is marketed as a supplement to support the structure and function of joints, and the marketing is targeted to people with osteoarthritis.[4][5][6][11] Commonly sold forms of glucosamine are glucosamine sulfate,[4] glucosamine hydrochloride, and N-acetylglucosamine.[4][3] Of the three commonly available forms of glucosamine, only glucosamine sulfate is given a "likely effective" rating for treating osteoarthritis.[4] Glucosamine is often sold in combination with other supplements such as chondroitin sulfate and methylsulfonylmethane.[4][5][6]

Glucosamine, along with commonly used chondroitin, is not routinely prescribed to treat people who have symptomatic osteoarthritis of the knee, as there is insufficient evidence that this treatment is helpful.[4][5][12]

As is common with heavily promoted dietary supplements, the claimed benefits of glucosamine are based principally on individual clinical and laboratory studies. Clinical studies on glucosamine efficacy are divided,[4][5] with some reporting relief from arthritic pain and stiffness, while most studies report no conclusive benefit above placebo.[4][5][12][13][14]