If you do not have fresh blueberries, you can use frozen ones. We love how vibrant the smoothie turns out with frozen berries. Note that the smoothie will be a lot thicker with frozen berries, so you will need to add an additional 1/4 cup of milk to thin it out when blending. Same goes for bananas. Add 1/4 cup extra milk for frozen bananas. If using frozen blueberries (or bananas) we like to use the stirring paddle that came with our blender to help get the chunks mixed down into the liquid. If you do not have one, make sure to turn off the blender before removing the lid and stirring with a spoon.