1,500 mg/day of glucosamine sulfate, sustained for several weeks. The sulfate form seems to be the best.
Small and disputed benefit (greater with the brand-name sulfate).
View the study (meta-analysis) →Its regular use is associated with lower mortality; it does not demonstrate cause and effect.
View the study (cohorts) →⏱ 3 min read
Glucosamine is an amino sugar that the body synthesizes naturally and that serves as a building block of the glycosaminoglycans of articular cartilage, tendons, intervertebral discs, and other connective tissues; commercial supplements are industrially extracted from the exoskeleton of crustaceans (crab, shrimp, prawn) or, in non-animal alternatives, from bacterial fermentation of corn starch, and come in two main chemical forms with slightly different profiles: glucosamine sulfate and glucosamine hydrochloride.
The two forms are not interchangeable: glucosamine sulfate is the one with practically all the positive clinical evidence in osteoarthritis and the one with pharmaceutical recognition in several European countries (Dona, Xicil), whereas the hydrochloride (cheaper and dominant in the American market) has consistently worse clinical results in head-to-head trials, a critical distinction for understanding the heterogeneity of the available evidence.
The classic indication is knee and hip osteoarthritis, and the evidence is paradoxical: broad meta-analyses of heterogeneous trials (which mix both chemical forms) show modest or null effects on joint pain, whereas trials restricted to pharmaceutical glucosamine sulfate (1,500 mg/day in a single dose) show significant pain reductions and functional improvements comparable to some mild anti-inflammatory drugs.
The MOVES trial, published in Annals of the Rheumatic Diseases in 2016, compared glucosamine+chondroitin vs. celecoxib for 6 months in 606 patients with knee osteoarthritis and found comparable efficacy; other trials have shown that prolonged supplementation (at least 2-3 years) could also slow the structural progression of cartilage, measured by joint space narrowing on X-ray, a property that some would distinguish as disease-modifying.
The most studied combination on the market is glucosamine 1,500 mg/day + chondroitin 1,200 mg/day, a synergy based on the logic of combining two structural components of cartilage; head-to-head trials comparing the combination vs. each one separately do not show clear additive superiority, but the combination is the most widely used formulation in the real world and the one with the most efficacy and safety data under usual clinical use.
Beyond symptomatic relief, several 2-3 year trials have suggested that glucosamine sulfate may slow the radiographic progression of osteoarthritis, a property that makes it a "disease-modifying" compound (DMOAD) rather than a simple analgesic; these data are what led several European guidelines (EULAR, ESCEO) to classify it as a SYSADOA and American guidelines (ACR) not to recommend it, a difference in interpretation of the evidence that reflects different regulatory contexts.
The effective dose is 1,500 mg daily of pharmaceutical glucosamine sulfate (not hydrochloride), ideally in a single dose with a meal (divided doses have equivalent bioavailability but worse adherence); the clinical effect typically appears within 4 to 8 weeks and persists for as long as treatment continues, with no dependence or rebound on stopping; a minimum of 3 months of trial is advisable before judging individual response, which is heterogeneous.
Generally well tolerated; the most frequent adverse effects are mild digestive discomfort (dyspepsia, nausea, occasional diarrhea or constipation); people with shellfish allergy may have cross-reactions with crustacean-derived glucosamine (although the real risk is low because the allergy is to proteins and glucosamine is an amino sugar), so it is advisable to choose plant-based glucosamine in these cases; people taking warfarin should exercise caution because of a described interaction (potentiation of the anticoagulant effect), and caution is advisable in people with diabetes, in whom variable effects on blood glucose have been described, although most studies show no significant problems.
Information, not medical advice. Scientific evidence reflects the quality of the studies.