on both sides.
The goal is to stimulate evenly so that there won't be some larger ones running off on their own and smaller ones unable to catch up.
So let's say you need to inject 450IU Gonal-F a day, you do 225 in the morning, right side, then 225 in the afternoon, left side. If you need 150 Menopur on top of that, you can do 75 on left and 75 on right.
This down side is you do get more shots. The reason for doing this, particularly later in the stim phase is, the larger ones tend to absorb most of the injection, and everyone has a stronger vs weaker ovary, you want them to perform evenly so as to harvest more eggs. This is only valid for med to high stims. If you are doing 150, then don't bother, the dosage is too small to make a difference for our age any way.