Glucosamine Toxicity

Glucosamine is a naturally occurring amino sugar that is produced in your body and is important in the formation of proteins and lipids that form cartilage, the tough connective tissue that cushions your joints. Glucosamine is classified as a monosaccharide, a carbohydrate containing one molecule of sugar, and is used as a nutritional supplement to improve joint health and function. Despite its potential benefits, glucosamine may cause certain side effects. As with any nutritional supplement, consult your physician before using a supplement containing glucosamine.

Glucose Metabolism

According to a study published in January 2006 in the "American Journal of Physiology," high doses of glucosamine supplementation may contribute to a worsening of the symptoms of diabetes by interfering with the normal regulation of the hexosamine biosynthesis pathway, or HBP. The HBP helps your body break down glucose, or blood sugar, for energy. By interfering with the function of the HBP, glucosamine may contribute to the development of insulin resistance, which may increase your risk of developing diabetes and increase the severity of the disease once you have it.

Allergy

According to the U.S. National Library of Medicine, the majority of glucosamine products sold as nutritional supplements in the United States are derived from shellfish, particularly the shells of shrimp and crab. As a result, individuals with an allergy to shellfish may experience an allergic reaction when supplementing with glucosamine. Although the National Library of Medicine states that an allergic reaction to the shellfish components of glucosamine supplements are rare, the Mayo Clinic states that some reactions may occur, such as throat swelling, which may lead to difficulty breathing and is a medical emergency.

Drug Interactions

According to the University of Maryland Medical Center, glucosamine supplementation may interfere with some medications. Glucosamine may increase the side effects associated with the use of non-steroidal anti-inflammatory drugs and with insulin used for diabetes. Consult your physician if you are taking these drugs to make sure glucosamine supplementation will not cause any adverse reactions.

Other Considerations

According to the Mayo Clinic, glucosamine supplementation may cause mild side effects, although it is generally well tolerated by most adults. The most common side effects are an upset stomach, drowsiness, insomnia, headache, skin rash, sun sensitivity, nail toughening, abdominal pain, loss of appetite, vomiting, nausea, gas, constipation, heartburn, and diarrhea. In rare cases, glucosamine may cause a temporary increase in your heart rate and blood pressure, as well as heart palpitations. Consult your doctor about these side effects.