[2] Produced commercially by the hydrolysis of shellfish exoskeletons or, less commonly, by fermentation of a grain such as corn or wheat, glucosamine has many names depending on country.

[citation needed] 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.

[7][8] As is common with heavily promoted dietary supplements, the claimed benefits of glucosamine are based principally on clinical and laboratory studies.

[16] Another concern has been that the extra glucosamine could contribute to diabetes by interfering with the normal regulation of the hexosamine biosynthesis pathway,[17] but several investigations found no evidence that this occurs.

[18][19] Other studies conducted in lean or obese subjects concluded that oral glucosamine at standard doses does not affect insulin resistance.

[25] To meet the demands of vegetarians and others with objections to shellfish, manufacturers have brought glucosamine products to market made using fungus Aspergillus niger and from fermenting corn.

[36] In August 2012, a class-action lawsuit was filed in New York claiming that 21st Century Healthcare, Inc. had falsely advertised that its "Glucosamine 750 Chondroitin 600 Triple Strength" dietary supplements would restore lost cartilage.

[37] In April 2013, a San Diego man launched a proposed class-action lawsuit in California Federal Court accusing Nutramax Laboratories, Walmart and Rite Aid of falsely advertising the effectiveness of glucosamine.

[45] A trial of oral combination capsules (glucosamine, chondroitin, and manganese ascorbate) in dogs with osteoarthritis found no benefit on either gait analysis or subjective assessments by the veterinarian or owner.

[47] Another study examined both the serum and the joint synovial fluid after nasogastric (oral) or intravenous administration of 20 mg/kg glucosamine hydrochloride to eight adult horses.

The authors calculated that these glucosamine synovial fluid levels achieved by the oral route were 500 times lower than that required to have a positive effect on the metabolism of cartilage cells.

[49] They concluded that these higher synovial fluid levels obtained with the sulfate derivative were still too low to have a relevant biological effect on articular cartilage.