Glucosamine is a chemical found in the body. Glucosamine supplements are sold as glucosamine sulfate, glucosamine hydrochloride, and N-acetyl glucosamine. 

Glucosamine is used by the body to make other chemicals that build tendons, ligaments, cartilage, and the fluid that surrounds joints. Joints are cushioned by the fluid and cartilage around them. Taking glucosamine might increase the cartilage and fluid around joints and/or help prevent their breakdown.

People commonly use glucosamine sulfate and glucosamine hydrochloride for osteoarthritis. Glucosamine is also used for joint pain, rheumatoid arthritis, multiple sclerosis, and many other conditions.