psyllium
3 interactions related to psyllium
psyllium + metformin
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 + warfarin
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.
levothyroxine + fiber
Dietary and supplemental fiber can bind levothyroxine in the gut and modestly reduce how much of each dose is absorbed. When fiber intake is high or variable around the time of dosing, this can nudge TSH upward and make a stable dose harder to settle on. The effect is real but generally modest, and it is managed mainly by timing and consistency rather than by avoiding fiber.