Glucosamine
Summary
Glucosamine is one of the most-tested joint supplements. In the GAIT trial (1,583 people), 1,500 mg/day did not reduce knee pain more than placebo, and a network analysis of 10 large trials (3,803 people) found no clinically relevant effect on pain or joint-space narrowing. Case reports link it to higher INR with warfarin.
Key facts
How it works
ProposedGlucosamine is a building block for glycosaminoglycans in cartilage; supplement effects on cartilage have been proposed but not confirmed in large trials.[2]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Joint pain and joint-space narrowing | No effect | No effect | Meta-analysis · n = 3,803 · 2010 People with knee or hip osteoarthritis in 10 large trials Form: Glucosamine, chondroitin or both · Dose: Varied across trials · Duration: Varied across trials Compared with placebo, effects on pain and joint-space narrowing were below clinically relevant thresholds; industry-independent trials showed smaller effects. | 20847017 (opens PubMed)Source [2] |
| Knee osteoarthritis pain (20% reduction) | No effect | No effect | RCT · n = 1,583 · 2006 Adults with symptomatic knee osteoarthritis Form: Glucosamine hydrochloride, chondroitin sulfate, or both · Dose: 1,500 mg/day glucosamine; 1,200 mg/day chondroitin · Duration: 24 weeks Glucosamine and chondroitin, alone or together, were not significantly better than placebo for knee pain overall. | 16495392 (opens PubMed)Source [1] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Glucosamine sulfate | Varies | No head-to-head human absorption data in the sources cited here. | Adverse events were similar to placebo in pooled trials.[3] | Several European trials |
| Glucosamine hydrochloride | Varies | No head-to-head human absorption data in the sources cited here. | Tolerated in the 24-week GAIT trial.[1] | GAIT trial |
Studied doses
Doses studied in human trials ranged from 1,500 mg/day of glucosamine alone to 1,500 mg/day plus 1,200 mg/day of chondroitin sulfate, for 24 weeks in GAIT and longer in other large trials.[1][2]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- WarfarinCase reportCase reports and MedWatch reports describe a raised INR when glucosamine was added to warfarin.[4]
Who should be careful
- People on warfarin
- Raised INR has been reported after adding glucosamine.[4]
- Shellfish allergy
- Much glucosamine is extracted from shellfish shells, and people with a shellfish allergy may react to it; shellfish-free versions exist.[6]
- Diabetes
- NCCIH notes glucosamine may raise blood sugar in some people.[5]
- Pregnancy and breastfeeding
- Little is known about safety in pregnancy or breastfeeding.[5]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Frequently asked questions
Does glucosamine work for knee pain?
Large independent trials found no meaningful benefit over placebo.[1][2]
Glucosamine sulfate or hydrochloride?
Both forms have been tested; the pooled analysis found effects below clinically relevant levels overall.[2]
Is glucosamine safe with warfarin?
Raised INR has been reported, so this combination needs a clinician’s input.[4]
Is glucosamine made from shellfish?
Many products are made from shellfish shells and others by fermentation; labels list the source.
Sources
- [1]Glucosamine, chondroitin sulfate, and the two in combination for painful knee osteoarthritis.. N Engl J Med, 2006. RCT
- [2]Effects of glucosamine, chondroitin, or placebo in patients with osteoarthritis of hip or knee: network meta-analysis.. BMJ, 2010. meta-analysis
- [3]Effectiveness and safety of glucosamine and chondroitin for the treatment of osteoarthritis: a meta-analysis of randomized controlled trials.. J Orthop Surg Res, 2018. meta-analysis
- [4]Potential glucosamine-warfarin interaction resulting in increased international normalized ratio: case report and review of the literature and MedWatch database.. Pharmacotherapy, 2008. review
- [5]Glucosamine and Chondroitin for Osteoarthritis: What You Need To Know. National Center for Complementary and Integrative Health (NCCIH), 2023. fact-sheet
- [6]Glucosamine. Merck Manual Consumer Version, 2025. review
What changed
- Added shellfish allergy, blood sugar and pregnancy notes.
- First draft. Every PMID checked against NCBI E-utilities (title, journal and year taken from the PubMed record) and each evidence row written from its PubMed abstract.