A pharmaceutical composition composed of a dietary fiber composition composed of from about 48% to about 90% (w/w) glucomannan, from about 5% to about 20% (w/w) xanthan gum, and from about 5% to about 30% (w/w) alginate in combination with at least one of metformin or sitagliptin or a combination thereof is described. The pharmaceutical composition is effective to lower elevated blood glucose levels and total blood cholesterol levels in a subject significantly more than the dietary fiber composition alone or a composition consisting of at least one of metformin or sitagliptin or a combination thereof.