Sometimes our Pharmacy does not have enough vials. We are using Fiasp and pick up a handful vials at a time so I get that it (Fiasp) probably is not heavily used (at least locally). But even with the Humalog and Novolog, it would happen sometimes (that we were asked to come back a couple days later).
It was never a big deal as I would never wait until we are about to run out. So if they said they were running low, I am completely fine with them hanging onto the last couple vials in case somebody with a more urgent need comes in to the store after me.
I just go back in 2 or 3 days and pick them up.
Lately they have been filling on the spot so maybe they have increased the level they stock or maybe I am just getting lucky.
Our usage includes waste insulin as we do not recapture leftover insulin from the old cartridge.