Glucosamine and Chondroitin: Benefits, Dosage, and Safety

What glucosamine and chondroitin is

Glucosamine and chondroitin are structural constituents of cartilage, the connective tissue that cushions joints. Glucosamine is a building block for glycosaminoglycans that form part of cartilage structure, and chondroitin is a cartilage component that helps it resist compression. In the United States they are sold as dietary supplements, alone or in combination; glucosamine is sold as glucosamine sulfate or glucosamine hydrochloride, and chondroitin as chondroitin sulfate. In some other countries certain preparations are sold as prescription drugs. They are among the most commonly used supplements by adults diagnosed with osteoarthritis.

What it does

• Glucosamine is a building block for glycosaminoglycans that are part of the structural matrix of cartilage
• Chondroitin is a component of cartilage that contributes to its resistance to compression
• Both are natural constituents of joint cartilage and connective tissue
• Taken as supplements they are studied for effects on joint pain and function in osteoarthritis, though benefit is not established

Intake and dosing

Glucosamine and Chondroitin is not an essential nutrient, so no Recommended Dietary Allowance or Tolerable Upper Intake Level has been set. Doses in studies vary widely. Because supplement doses are not standardised, discuss an appropriate amount with a clinician or pharmacist.

Deficiency and who is at risk

Not applicable. Glucosamine and chondroitin are not essential nutrients and have no defined dietary requirement, so there is no recognized deficiency state or deficiency syndrome. The body synthesizes glucosamine endogenously.

Who may need more

• Adults with knee or other osteoarthritis who choose to try a supplement, recognizing that NIH-reviewed evidence for benefit is inconsistent and major guidelines differ
• No one requires these for nutritional adequacy; they are not essential nutrients
• People with shellfish allergy should check the source, since glucosamine is often derived from shellfish
• People taking warfarin should consult a clinician before use because of bleeding risk
• People with diabetes or elevated blood sugar should monitor glucose, as glucosamine may raise blood glucose in some individuals

Food sources

Not obtained from ordinary foods in meaningful amounts. Supplemental glucosamine is typically manufactured from the shells of shellfish (or produced synthetically), and chondroitin is typically derived from animal cartilage. There is no established dietary food source.

Forms and absorption

Glucosamine is sold as glucosamine sulfate or glucosamine hydrochloride; chondroitin is sold as chondroitin sulfate. They are available separately or as a combination product. Some studies suggest results may differ between prescription/pharmaceutical-grade crystalline glucosamine sulfate formulations (sold in some countries) and over-the-counter formulations, though this may reflect differences in study quality or bias rather than proven product superiority. Product content can vary between brands.

Safety, excess and interactions

Too much

No major safety problems have been identified in large osteoarthritis studies. Reported effects at supplement doses are generally mild, infrequent, and similar to placebo, and may include gastrointestinal upset such as nausea, heartburn, or diarrhea. Glucosamine may raise blood glucose (sugar) levels in some people. No Tolerable Upper Intake Level has been established, and there is no established toxicity threshold.

Interactions to know

• Warfarin: glucosamine and chondroitin, alone or together, have been associated with an increased risk of bleeding in people taking the anticoagulant warfarin; INR should be monitored and a clinician consulted
• Antidiabetes medications / blood glucose: glucosamine may raise blood glucose levels in some people, which is relevant for people with diabetes or those on glucose-lowering therapy

How status is measured

Not routinely measured. There is no clinical laboratory marker for glucosamine or chondroitin status, and no deficiency state to test for.

Regulated in the United States as dietary supplements, not as drugs, and not approved by the FDA to treat, cure, or prevent any disease including osteoarthritis. No Dietary Reference Intake has been established. In some other countries certain glucosamine and chondroitin preparations are sold as prescription drugs.

What the evidence supports

We grade the strength of evidence behind each common reason people take glucosamine and chondroitin, mirroring how the NIH describes it.