Doctor's Best Glucosamine Sulfate supports joint structure, function and supplies the body with building blocks for healthy joints. Glucosamine is used for the biosynthesis of proteoglycans in healthy joints, which help maintain sound joint structure and healthy joint function. Potassium Sulfate is added to support the formation of sulfate linkages found naturally in the hydrocolloid chondroitin sulfate and proteoglycans. This formula is Non-GMO, Gluten Free, and Soy Free.