What is the maximum daily dosage for glucosamine?

The glucosamine dose that has been used in most research studies is 1500 milligrams once daily or divided into three equal doses. It is unknown whether there is a maximum daily dosage or toxic dosage for glucosamine. However, because glucosamine is often combined with other substances, the toxic effects of other ingredients must also be considered. For example, the element manganese is added to some glucosamine supplements because it may have a beneficial effect on cartilage (the cushion between bones that wears away in osteoarthritis). Chronic, high amounts of manganese (more than 11 milligrams per day) may cause drooling, memory loss, confusion, hallucinations, trembling and other symptoms.