Glucosamine hydrochloride (glucosamine HCl) is the most common form of glucosamine found in supplements. However, studies using glucosamine HCL have reported mostly nonsignificant results, suggesting that this form may not be as effective as other forms, particularly glucosamine sulfate.[1][2]
In comparison, glucosamine sulfate is thought to be more bioavailable when taken orally and has a reduced clearance from the body compared to glucosamine HCL.[3]
There is also a form of glucosamine available as a glucosamine sulfate-sodium chloride complex, with a 2:1:1:2 ratio of glucosamine:sulfate:chlorine:sodium. This formulation, patented by Rottafarma in Germany, is designed to be taken once a day; it is sometimes referred to as the “Rotta formulation”.[4] One study compared the pharmacokinetics of the Rotta formulation and glucosamine sulfate, and found no significant difference.[5] In terms of its efficacy, it’s still unclear whether this glucosamine sulfate salt complex is any more effective than glucosamine sulfate, and further research is needed to determine their comparative efficacy.