I am not sure I would try mixing Metamucil without water. Metamucil gets gel-ly when mixed with liquid, so you need the extra water to wash it down. You also have to drink it fairly quickly, so unless you can "down" your smoothie really fast, I wouldn't do it.In my smoothies I add Unifiber, which I bought at KMart. It's powdered plant cellulose. It can be mixed with foods and does not alter the taste and does not need to be followed with lots of water. Another option would be Benefiber, which is guar gum. That, too, can be added to foods and does not need to be consumed with water. Although a little water always helps the fiber do it's thing. Both of these fibers are about $10 a bottle, much more than generic Metamucil, but much better for your purposes.If you are also talking about taking Fiber Delights, which are inulin fiber, go to the Constipation board and look under the past posts.