Supposedly once an insulin vial is opened, it is only good for 30 days and should be discarded. I have thrown away more than 100 vials of half used insulin, because my child only uses half of it by the 30th day. We pay full price. Why don't they make a child sized vial and price it accordingly? Because the pharmaceutical company would lose millions of dollars a month. (approximately 250 million or more; a quarter of a billion dollars a month).