Because glucosamine is produced naturally by the body, adverse reactions are minimal. To date, the safety profiles of glucosamine formulations in randomized clinical trials have been excellent compared to other NSAIDS. In one study of 1486 randomly selected people, only seven withdrew because of glucosamine-related side effects.[13] However, mild nausea, heart burn, constipation, abdominal bloating, and diarrhea were reported by small percentages of participants in larger clinical trials.

Cautions

Although glucosamine is produced by the body, there are some cautions that should be observed when adding additional glucosamine. Use caution if any of the conditions below apply to you.

• If you're on a potassium restricted diet Glucosamine sulfate is stabilized by potassium chloride. The typical daily dose of glucosamine contains over 2.5 mg of potassium. That's slightly more than half a banana (2.5 mg per gram) or 4 slices of whole grain bread. Higher than usual potassium levels may be hazardous for people who have malfunctioning kidneys. Talk with your doctor. Also, the use of certain diuretics may be a reason to restrict your intake of potassium.
• Allergy: Glucosamine is derived from the shell of a shellfish. People who are allergic to shellfish may experience an allergic reaction. Although meat is removed prior to the use of the shell, the possibility of an adverse reaction cannot be ruled out completely. Talk to your physician or allergist with any questions about your condition before using glucosamine.
• Diabetes: Glucosamine comes from glucose, a naturally occurring sugar. Some scientific studies have shown that glucosamine may, in some cases, increase blood glucose levels in animals. This was observed after glucosamine infusion at a very high dosage. It was shown not to occur after oral administration of the usual dosage in healthy humans. To be on the safe side, diabetics should monitor their blood sugar more regularly and discuss the use of glucosamine with their physician.
• Pregnancy: Do not use glucosamine during pregnancy or when you wish to get pregnant. Glucosamine has a favorable safety profile but hasn't been evaluated for taking during pregnancy.