Glucosamine salts contain the low molecular weight glucosamine that must first be acetylated to N-acetylglucosamine before it can be used as a building block for macromolecules. The acetylation process is rate limiting. Substances such as alcohol and NSAIDs may slow or prevent the acetylation process.
From Glucose to Hyaluronic Acid: Where the different glucosamines enter the human metabolic pathway.