You may have added too much milk with not enough ice cream. If that’s the case, for a thicker consistency, just add more ice cream. Also, if you end up with extra milkshakes because you had to add more ice cream, you can freeze the leftovers and have another milkshake on a different day. It will be frozen, so you can take it out of the freezer and let it set on the cupboard for a few minutes, or just dive into it with a spoon.  Frozen milkshakes are the yummiest of yums!