Glucosamine

What is glucosamine and what does it do in the body?

According to NCCIH, glucosamine and chondroitin are components of the cartilage in joints; glucosamine is a building block of molecules called glycosaminoglycans, which are part of the cartilage structure. ^[1] That the compound is found in cartilage does not mean that glucosamine taken by mouth rebuilds worn cartilage; this is “role in the body” information, and the effect of the supplement is measured separately. The outcomes measured in studies are mostly symptoms such as pain, function, and joint space in knee osteoarthritis, and imaging variables. ^[1]

Osteoarthritis is a degenerative joint disease in which cartilage and other tissues in the joint deteriorate; its symptoms are pain, stiffness, swelling, and difficulty moving; it most often affects the knees, hips, and hands. According to NCCIH, the disease has no cure, but approaches such as weight loss and physical activity help manage symptoms. ^[1]

In what forms and from what sources is glucosamine found?

In the US, glucosamine (as sulfate or hydrochloride) and chondroitin (as chondroitin sulfate) are sold as dietary supplements, separately or together; in some countries, certain glucosamine and chondroitin preparations are prescription drugs. ^[1] This distinction directly affects how the evidence is interpreted: the Cochrane review analyzed studies involving a single manufacturer’s glucosamine preparation separately from studies involving other preparations (the review names the manufacturer). ^[2]

In Türkiye, the Ministry of Agriculture and Forestry’s Restricted Substances List names shellfish (crab, lobster, shrimp) and cattle as sources for glucosamine sulfate; Aspergillus niger fermentation for glucosamine hydrochloride and glucosamine sulfate KCl; and, in the “other sources” rows, shrimp, crab, and chemical synthesis for glucosamine HCl, and chemical synthesis, cattle, and shrimp for glucosamine sulfate KCl. ^[13]

Does glucosamine help pain in knee osteoarthritis?

Short answer: the results conflict, and the picture varies with which product and which studies are selected.

Cochrane review (2005)

The Cochrane update by Towheed and colleagues analyzed 20 randomized studies (2,570 patients). When limited to the 8 studies with adequate allocation concealment, the benefit of glucosamine for pain and WOMAC function could not be shown. When all 20 studies were taken together, SMD for pain was −0.61 (95% CI −0.95 to −0.28); however, it was noted that the results were not consistent and the reason could not be explained. In the 10 studies comparing a single manufacturer’s preparation with placebo, SMD for pain was −1.31 (−1.99 to −0.64), whereas in studies involving other preparations it was −0.15 (−0.35 to 0.05), and the latter did not reach significance. The proportion of participants reporting adverse events was similar to placebo (RR 0.97; 95% CI 0.88–1.08). ^[2]

Results that diverge by manufacturer (Eriksen 2014)

Eriksen and colleagues examined 25 placebo-controlled studies (3,458 patients): the overall effect was SMD −0.51 (−0.72 to −0.30), but heterogeneity between studies was very high (I² 88%). The factor that most explained the heterogeneity was the product brand. In 12 studies using a single manufacturer’s product (1,437 patients), SMD was −1.07 (−1.47 to −0.67); when restricted to 3 studies at low risk of bias, SMD was −0.27 (−0.43 to −0.12), that is, a small effect. In 13 studies using other products (1,963 patients), no reduction in pain was seen (SMD −0.11; −0.46 to 0.24). ^[3] NCCIH notes that most studies done with the prescription form were at high risk of bias, more than 20 years old, and funded by a pharmaceutical company. ^[1]

Individual-participant-data analysis of independent studies (Runhaar 2017)

In the analysis by the OA Trial Bank using individual participant data, 6 of 21 eligible studies shared their data (n=1,663); 5 of them were industry-independent and compared glucosamine with placebo (n=1,625; 55% of participants in published placebo-controlled studies). Glucosamine was no better than placebo for pain and function at months 3 and 24; no difference was seen in the subgroups of pain severity, BMI, sex, structural damage, and inflammation. Splitting by knee osteoarthritis and by glucosamine type did not change the result. ^[4]

GAIT (2006)

The 24-week GAIT study in the US, which enrolled 1,583 patients with knee osteoarthritis (mean age 59; 64% women), compared glucosamine, chondroitin sulfate, both together, celecoxib, and placebo. The primary outcome was a 20% reduction in knee pain; the response rate in the placebo group was 60.1%. In the glucosamine group the rate was 3.9 points higher (P=0.30); in the combination 6.5 points (P=0.09); with celecoxib 10.0 points (P=0.008). In the subgroup of 354 patients with moderate-to-severe pain, the combination gave a response rate of 79.2% versus 54.3% with placebo (P=0.002); the authors describe this as an exploratory analysis. ^[5]

Network meta-analysis (Wandel 2010)

Wandel and colleagues pooled 10 studies with more than 200 patients each (3,803 patients). On a 10 cm visual analog scale, the pain difference was −0.4 cm for glucosamine (95% credible interval −0.7 to −0.1), −0.3 cm for chondroitin, and −0.5 cm for the combination; the prespecified threshold for a clinically important difference was −0.9 cm, and no estimate’s interval reached this threshold. In industry-independent studies, effects were smaller than in commercially funded studies (interaction P=0.02). The authors concluded that health authorities and insurers should not cover the cost of these preparations. ^[9]

Does glucosamine protect cartilage or affect joint space?

The evidence is inconsistent. In the 3-year study by Reginster and colleagues (212 patients; 1,500 mg/day glucosamine sulfate or placebo), mean joint space loss was −0.31 mm (−0.48 to −0.13) in the placebo group versus −0.06 mm (−0.22 to 0.09) in the glucosamine group; WOMAC symptoms worsened slightly in the placebo group. ^[6] In the 24-month structural substudy of GAIT (572 patients; glucosamine 500 mg three times daily), no treatment group differed significantly from placebo; mean joint space loss in the placebo group was 0.166 mm, and the authors noted that the study’s power was limited. ^[8]

In the 2-year LEGS study (605 participants, ages 45–75), the combination reduced joint space narrowing by a mean of 0.10 mm (95% CI 0.002–0.20; p=0.046) compared with placebo; no significant structural effect was found for glucosamine alone. For pain, all four groups improved in the first year and there was no significant difference between groups (p=0.93). ^[7] In Wandel’s network meta-analysis, the differences in joint space were found to be “very small,” and the credible intervals included zero. ^[9] NCCIH states that the effect of glucosamine and chondroitin on joint structure is uncertain. ^[1]

Glucosamine in hip and hand osteoarthritis

As relayed by NCCIH, the AAOS 2017 hip osteoarthritis guideline concluded that moderate-strength evidence does not support the use of glucosamine sulfate in hip osteoarthritis; this conclusion rests on a single high-quality study published in 2008 (222 people, 2 years), in which glucosamine was no better than placebo for pain, function, and joint space. ^[1] The ACR/AF 2019 guideline gave a strong recommendation against glucosamine in knee, hip, and/or hand osteoarthritis (“strongly recommended against”). ^[10]

What do guidelines say about glucosamine?

The comparison by Arden and colleagues summarizes the same contradiction: ESCEO recommends pharmaceutical-grade glucosamine and chondroitin sulfate, while OARSI gives a strong recommendation against all forms of glucosamine and chondroitin. ^[11]

Is glucosamine safe? Warfarin, blood sugar, and pregnancy

NCCIH states that no major safety problems were found in large studies of glucosamine and chondroitin. According to the same source, glucosamine may raise blood sugar in some people; glucosamine and chondroitin have been associated with increased bleeding risk in people using the anticoagulant warfarin; and little is known about their safety during pregnancy and breastfeeding. ^[1] The ACR/AF guideline also reports that the potential toxicity of glucosamine is low, but that some patients may show increases in serum glucose levels. ^[10] In the Cochrane review, the proportion of participants reporting adverse events was similar to placebo. ^[2]

The warfarin association rests on case reports and spontaneous reports. Knudsen and Sokol reported a 71-year-old man who had been taking warfarin for 5 years and, for the same period, a glucosamine hydrochloride–chondroitin sulfate combination: about 3 weeks after the supplement dose was increased, INR rose from 2.3 to 3.9; 16 days after the supplement dose was reduced, INR measured 4.7; and 16 days after the supplement was stopped and the warfarin dose also reduced, INR was 2.6. The same study identified, in the FDA MedWatch database, 20 reports of glucosamine or glucosamine–chondroitin used together with warfarin with altered coagulation, and, in the WHO database, 21 spontaneous reports of INR increases associated with glucosamine (resolution on stopping glucosamine in 17 of them). The authors state that more information is needed to define the interaction. ^[12]

How is glucosamine regulated in Türkiye?

In Türkiye, food supplements are regulated by the Ministry of Agriculture and Forestry, and Ministry approval is mandatory for every food supplement to be placed on the market. ^[14] In the “daily intake dose for ages 11 and older” column of the Ministry’s Restricted Substances List (last updated September 21, 2026), an upper limit of 1,500 mg/day is given for glucosamine sulfate, glucosamine HCl, and glucosamine sulfate KCl; the ages 4–10 column is empty in these rows. ^[13] The first publication date for glucosamine sulfate is January 22, 2016; the list also requires the following label warnings: “18 yaş altı bireylerde kullanılmaz.” (not for use by individuals under 18) and “Bu takviye edici gıdanın 3 aydan fazla kullanılması durumunda doktora danışılmalıdır.” (a doctor should be consulted if this food supplement is used for more than 3 months). ^[13]

In the list, the Aspergillus niger-sourced rows appear on the condition that they “comply with Annex-1 of the Turkish Food Codex Novel Foods Regulation”; for the “other sources” rows, there is a note that “if it is proven that it was used in food supplements before December 31, 2025, it will not be evaluated under novel foods.” According to the footnote of the list, compliance of components under Provisional Article 1 of the Novel Foods Regulation with Annex-1 must be ensured by June 30, 2027. ^[13] This list is an upper limit; it does not mean the product is effective.

Evidence table: claim, population, and limits