Glucosamine is an amino monosaccharide that is found in high concentrations in connective tissues and cartilage, where it helps synthesize glycoproteins and glycosaminoglycans, which are essential for the elasticity and strength of these tissues. Although they are not FDA approved, glucosamine supplements are often used for osteoarthritis management, though studies on their effectiveness have yielded mixed results.

Glucosamine is primarily used as a supplement for osteoarthritis, and some studies suggest that it may reduce knee arthritis severity and improve stiffness, though evidence of its effectiveness is mixed and often criticized. Additionally, it may help reduce pain in people with temporomandibular joint disorder after prolonged use, but overall scientific support for its benefits remains limited.

Glucosamine is generally safe, with minimal side effects (primarily gastrointestinal issues) and no significant difference in side effects compared to placebo. However, there was an isolated case in which glucosamine enhanced warfarin's anticoagulant effect, and animal studies suggest that it may increase insulin resistance, though more research is needed to clarify these effects.

Glucosamine works by interfering with the inflammatory processes that lead to collagen degradation in arthritic tissues, particularly by downregulating proinflammatory molecules like interleukin 1. Although it may also promote collagen expression through the synthesis of glycosaminoglycans, the concentrations studied were high and not necessarily applicable to typical human consumption, and clinical studies have not shown significant effects on collagen synthesis biomarkers.