Glucosamine is available in several forms. The glucosamine sulfate (GS) form (stabilized with a mineral salt) is the only form clearly shown in clinical trials to be effective for osteoarthritis. For this reason, it is the preferred form.
GS is stabilized with one of two mineral salts: sodium chloride (NaCl) or potassium chloride (KCl). Although they both appear to effectively stabilize GS, the use of KCl as a stabilizer seems preferable since the average Western diet already provides far too much salt (NaCl) and not enough potassium. However, most of the research has been done with the NaCl-stabilized form.
Concerns have been raised about the quality of GS products on the market. In one study, the amount of glucosamine contained in 14 commercially available glucosamine products varied from 41% to 108% of the amount stated on the label. Even when the weight of the sulfate molecule was included, 11 of the 14 products contained less than the amount of glucosamine stated on the label. Some manufacturers may include the weight of the stabilizing salts (NaCl or KCl) in the total weight of the product, without stating so on the label.
Glucosamine hydrochloride (GH) has been widely available as a dietary supplement for years, but only one trial has evaluated this form of glucosamine as a single remedy for OA. This trial found only minor significant benefits from 1,500 mg per day of GH for eight weeks, in people with osteoarthritis of the knee who were also taking up to 4,000 mg per day of acetaminophen. To more fairly evaluate the effects of GH, future research should involve people not taking pain-relieving medication.