Hypromellose, also known as hydroxypropyl methylcellulose (HPMC), is a synthetic polymer derived from cellulose. It is made by chemically modifying natural cellulose obtained from wood pulp or cotton fibers through a process known as etherification. In this process, the cellulose fibers are treated with a combination of propylene oxide and methyl chloride, which leads to the addition of hydroxypropyl and methyl groups to the cellulose molecules.

The resulting product is a water-soluble polymer that is used in a variety of applications, including pharmaceuticals, cosmetics, food products, and dietary supplements. Hypromellose is available in different grades, with varying molecular weights and degrees of substitution, depending on the intended use.

Overall, hypromellose is considered to be a safe and well-tolerated ingredient when used as directed. It is commonly used as a coating agent, a thickening agent, and a stabilizer in many products and is valued for its ability to improve product stability, increase viscosity, and enhance product performance.