The first is the expiry date of the drug itself. Usually two years, a year and a half to two years.

Another is the date of use. As long as the insulin is turned on, it's already been used. Be sure to mark the date of starting it.

Well, you know, why do you put the date on?

Insulin is effective within four weeks! Some people may take a small dose, a month may not be used up, that over a month can not be used. So be sure to note two dates, one is a valid date and the other is a use date to avoid expiration.