Add a tiny bit of apple cider vinegar to bring out all the sweetness of the fruit.
For some added healthy fats, you can either add some avocado, or nut butter. It adds some creaminess too.
If you looking for some extra flavour, why not add a little grated ginger to this grapefruit smoothie?
If you are using whole grapefruit rather than just juice, make sure you remove as much of the pith as possible, as this will make the smoothie bitter with too much of it.
If storing leftovers of the smoothie, give it a good shake or a little blend again before serving.