Follistim shortage??

My dr tried to order me 300 unit vials but all that was in stock was 600. So now I have 2 of those and I'm worry about wasting a lot if I only end up using a little bit out of the second vial! Anyone else having trouble getting the 300 or 900 vial? My insurance will only cover 3000 units in my lifetime and I would like to try this more than 2 times!