I always take my metamucil before I go to bed but if your taking your probiotic as well try to space them out. The reason for this is that the metamucil absorbs all the excess liquid in the colon and it binds the gunk off the colon walls. The probiotic you want it to stay in your colon and not be absorbed by the fibre, plus it's best to take the probiotic on an emplty stomach or a couple hours after you eat.