it is ok to mix it with milk although i never i makes my stomach puffy so i rather use water, i love to mix ti with a banana and some nuts in a blender and sometimes coffee.
I've heard mixing it with milk makes it hard for ur body to absorb it also the extra calories my be a problem depending on your goals.... Sure does taste good that way tho.. I mix a scoop in my oatmeal ialong with ground flax seed and a splash of 2%milk taste like pudding