There is some preliminary evidence suggesting that glucosamine, in doses used to treat osteoarthritis, may alter levels of blood sugar, insulin and/or hemoglobin A1C (a test that measures how well blood sugar has been controlled during the previous three months) in people with diabetes or insulin resistance.
Other studies, however, haven't found an effect. Until we know more, people with diabetes or hypoglycemia and those who are taking medication or supplements that affect blood sugar should use caution and only take glucosamine under the supervision of a qualified health professional.
Most studies involving humans have found that short-term use of glucosamine is well-tolerated. Side effects may include drowsiness, headache, insomnia, and mild and temporary digestive complaints such as abdominal pain, poor appetite, nausea, heartburn, constipation, diarrhea, and vomiting. In rare human cases, the combination of glucosamine and chondroitin has been linked with temporarily elevated blood pressure and heart rate and palpitations.
Theoretically, glucosamine may increase the risk of bleeding. People with bleeding disorders, those taking anti-clotting or anti-platelet medication, such as warfarin, clopidogrel, and Ticlid, or people taking supplements that may increase the risk of bleeding, such as garlic, ginkgo, vitamin E or red clover, should not take glucosamine unless under the supervision of a healthcare provider.
Since glucosamine supplements may be made from shellfish, people with allergies to shellfish should avoid glucosamine unless it has been confirmed that it is from a non-shellfish source. The source of glucosamine is not required to be printed on the label, so it may require a phone call to the manufacturer.
The safety of glucosamine in pregnant or nursing women isn't known.
