Fiber can sometimes bind to some supplements, such as iron, and render them ineffective, so it may do the same thing to some meds. (That's why you'll see Metamucil has extra added iron). I'd say take the fiber completely seperately from your supplements and meds. I'd take the fiber just before bedtime instead. Do you drink a large glass of water with lemon first thing in the morning? (Preferably not ice cold). If you have a problem with constipation you may find this will relieve the problem without adding the Metamucil. For my occasional problem I take chitosan. It is derived from crustacean shells and has zero carbs, but I rarely need it. Since I increased my water intake the constipation has gone away.