If you are taking chondroitin sulfate in addition to a blood-thinning medication or daily aspirin therapy , have your blood clotting time checked more often. This supplement is similar in structure to the blood-thinning drug heparin, and the combination may cause bleeding in some people. If you are allergic to shellfish , consult your doctor before deciding to take glucosamine. In most cases, however, allergies are caused by proteins in shellfish, not chitin, a carbohydrate from which glucosamine is extracted. Nevertheless, some degree of efficacy appears probable for these preparations.
Evidence is widely touted but incomplete.