http://www.mayoclinic.org/drugs-supplements/glucosamine/safety/hrb-20059572
Safety
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.
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Glucosamine is likely safe when taken by mouth in studied doses (500 milligrams three times daily up to 90 days or 1,500 milligrams once daily up to six months) for a short time by healthy adults. Glucosamine sulfate is likely safe when injected into the joint at recommended doses for up to six weeks (not available in the United States).
Glucosamine is possibly safe when taken by mouth in recommended doses for up to three years. Doses of up to 3 grams daily and higher have been used in people with osteoarthritis.
Use cautiously in women who are, or plan to become, pregnant, or are breastfeeding. Use cautiously in children under 18 years old.
Drowsiness or sedation may occur. Glucosamine may also cause insomnia. Use caution if driving or operating heavy machinery.
Use cautiously when taking recommended doses over a long time period or if injected into the muscle. Use cautiously if using doses higher than those recommended. Use cautiously in people with low blood platelet counts, as glucosamine may interact with antibodies.
Use cautiously in people who have asthma, kidney disorders, active peptic ulcer disease, depression, skin conditions, or in people who need to restrict potassium intake.
Use cautiously in people who are at risk for cataracts, or in older people who have dry eyes. Glucosamine may cause increased cataract risk or dry eyes.
Use cautiously in people taking agents that increase the flow of urine.
Glucosamine may increase the risk of bleeding. Caution is advised in people with bleeding disorders or taking drugs that may increase the risk of bleeding, such as vitamin K antagonists (warfarin). Dosing adjustments may be necessary.
Glucosamine may affect blood pressure. Caution is advised in people with high blood pressure or heart conditions, or those taking drugs or herbs and supplements that affect blood pressure. Glucosamine may cause abnormal heart rate and palpitations.
Glucosamine may affect insulin resistance and/or blood sugar levels. Caution is advised in people with diabetes or low blood sugar, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood sugar levels may need to be monitored by a qualified healthcare professional, including a pharmacist, and medication adjustments may be necessary.
Avoid using glucosamine-chondroitin supplements that contain Chinese skullcap. Liver damage has been reported with use of the Chinese skullcap contained in the Move Free® Advanced dietary supplement.
Avoid use with methylsulfonylmethane in children due to a potential link with autisim.
Avoid in people with a known allergy or sensitivity to glucosamine sulfate or its parts. Glucosamine comes from shrimp, crab, and other shellfish, and should be avoided if allergic or sensitive to shellfish or iodine.
Glucosamine may also cause anorexia, back or neck pain, changes in levels of creatine phosphokinase (enzyme found in heart, brain, and skeletal muscle), blood urea nitrogen, or creatine levels, constipation, coughing, diarrhea, dizziness, dry mouth, ear inflammation, a feeling of heaviness in the stomach, fluid accumulation, gas, headache, heartburn, increased blood lipids, increased growth rate of fingernails, indigestion, liver problems, muscle problems, nausea, stomach pain, toughened nails, upper abdominal tenderness, and vomiting.
Pregnancy and Breastfeeding
Use cautiously in women who are or plan to become pregnant, or those who are breastfeeding, due to lack of evidence.
