Psyllium Interactions

Psyllium's viscous gel can slow and reduce metformin absorption when taken together, potentially blunting its glucose-lowering effect, while psyllium's own action lowers glucose — making net blood-sugar effects variable.

Psyllium is a soluble fiber that forms a viscous gel in the gut, and it was long suspected of trapping warfarin and slowing its absorption. However, the limited human evidence available — a pharmacokinetic study and the monographs that cite it — found that psyllium does not measurably change warfarin's blood levels or its effect on the INR. Because warfarin has a narrow safety margin, keeping fiber intake steady and spacing the doses remains sensible, but a clinically meaningful interaction has not been demonstrated.