Psyllium is a bulk-forming fiber laxative. Psyllium works by absorbing liquid and swelling in the intestines to create a softer, bulky stool that is easier to pass. Psyllium is used to treat occasional constipation or bowel irregularity. Psyllium may also help lower cholesterol when used together with a diet low in cholesterol and saturated fat. Psyllium may also be used for purposes not listed in this medication guide.