Not sure to be honest. If you always get your repeat from the same chemist then maybe they'd be ok. Do you know them well enough to ask and let us know what they say. Running out can happen as we all can make mistakes from time to time.
However, you should not run out of insulin. At diagnosis I was advised to order a repeat when I still had 2 pens remaining. That ensures for the possible failure of one of the pens and still having insulin in the pen I am using.
Be sure to check that the insulin supplied by the chemist is long dated and that you are not being supplied with short dated stock.
As those above has already siad, you should not run so low you run out; but if so then a swift trip to the nearest A&E as an emergency until you can get a script filled.