Methylcellulose, carboxymethylcellulose, and hydroxymethylcellulose are forms of the familiar polysacharide cellulose, treated to make it more soluble in water. Cellulose is a long chain made of the sugar glucose. The long chains mix with water to make a thick syrup or gel. Methylcellulose is used as a thickener in sauces and salad dressings, and as a thickener and stabilizer in ice cream, where it helps prevent ice crystals from forming during freezing or re-freezing after a thaw.

Methylcellulose is a Bulk Forming Fiber Laxative . Bulk laxatives absorb liquid in the intestines and swell to form a soft bulky stool. The bulky mass stimulates the intestinal muscles speeding stool transit time through the colon. Methylcellulose will not work as a bulking forming laxative without increased fluid intake.