Glucosamine and chondroitin: do they help joints?

What are these products?

Glucosamine and chondroitin are substances related to the structure of cartilage, the tissue that helps cushion joints. Supplements come separately or together, and glucosamine sulfate and hydrochloride are different preparations. Some countries also have prescription formulations. A substance occurring in cartilage does not mean swallowing it rebuilds cartilage; trials of one preparation do not automatically establish the effects of another.1

What did a large knee trial find?

The 2006 US GAIT trial randomly assigned 1,583 adults with painful knee osteoarthritis to glucosamine hydrochloride, chondroitin, both, a prescription pain medicine or placebo for 24 weeks. Its main outcome was at least a 20% reduction in knee pain. Overall, neither supplement alone nor their combination performed significantly better than placebo. About 60% of the placebo group reached the response threshold; improvement after taking a product does not by itself show the product caused it.

An exploratory analysis suggested benefit from the combination in participants with moderate-to-severe pain. A subgroup finding needs confirmation and does not establish that the combination works for everyone with severe pain. The study did not test every formulation.

Among the 354 participants classified with moderate-to-severe pain at the start, spread across all five treatment groups, 79.2% in the combined-supplement group and 54.3% in the placebo group reached the trial’s pain-response threshold. These are proportions reaching at least a 20% reduction, not average pain reductions. The subgroup comparison involved fewer people and was exploratory, so the larger difference could be less reliable than it appears and needs confirmation in further studies. The trial was funded by the US National Institutes of Health.2

Why do guidelines differ?

The US National Center for Complementary and Integrative Health describes inconsistent study results and uncertainty about symptoms and joint structure. The UK NICE guideline says not to offer glucosamine for osteoarthritis because there is no strong evidence of benefit. The 2026 US Veterans Affairs and Department of Defense guideline found insufficient evidence to recommend for or against glucosamine, chondroitin or their combination for knee or hip osteoarthritis. The American College of Rheumatology’s 2026 summary strongly recommends against glucosamine, chondroitin and their combination for osteoarthritis of the knee, hip or hand. A strong recommendation describes the panel’s judgment about a course of action; it does not mean every underlying study is equally certain. These are different evaluations of evidence and apply to the conditions specified, not proof that every formulation has identical effects.

Neither an improvement in pain nor a change in joint-space measurement alone proves cartilage has been rebuilt. Other products have their own evidence: compare turmeric and curcumin and collagen supplements.1345

What about safety and interactions?

Glucosamine and chondroitin have been associated with an increased risk of bleeding in people taking warfarin. Glucosamine may increase blood glucose in some people; safety in pregnancy and breastfeeding is not well established. Product ingredients and personal health conditions matter. Ask a pharmacist or clinician about a particular product and medicines, and do not stop a prescribed blood thinner on your own. Persistent joint pain deserves assessment. For more context, see supplement interactions and the nutrition hub.1

Some glucosamine is made from shellfish shells. If you have a shellfish allergy, check the exact product and ask a pharmacist or allergy specialist before using it; products do not all have the same source. Shell-derived material may contain traces of shellfish allergens.6