Expiry dates and stock rotation
Insulin has two dates, and the second starts when you open it. Plus the items that expire quietly: ketone strips and glucagon, checked only when already needed.
Insulin has two dates, not one, and the second is the one people miss. There is the expiry printed on the box, and there is a much shorter clock that starts the moment a pen goes into use. Everything else in your kit has dates too, and the ones you use least often are the ones most likely to have run out.
- The printed expiry is for unopened stock. Once in use, a separate and much shorter clock starts.
- Write the date on the pen when you start it. Nobody remembers that reliably.
- Ketone strips and glucagon are the items most likely to be out of date at the exact moment you need them.
- New stock goes behind old. One habit, applied at the point of unpacking, removes most of this.
- Running your own stock is yours; insulin that seems to have stopped working is a conversation with your diabetes team.
The one on the box, and the one that starts when you open it
The printed expiry describes unopened supplies kept properly, and it is usually a long way off. That is why people stop thinking about dates: the number on the box says next year, so the question feels answered.
The second clock is the one that runs out. Once a pen or vial is in use and living at room temperature, it stays reliable for a limited period stated in the leaflet for that specific insulin, and it differs between them. After that it can gradually lose strength while looking exactly the same, so there is nothing to notice.
The fix is a marker pen. Writing the date you started it on the pen itself, or a note on your phone, turns a thing you have to remember into a thing you can read. Left to memory, the estimate almost always runs long, because a pen with insulin still in it does not feel like a problem. If a pen has been living in a bag or a hot car, where it has been matters as well as how long, and that is covered separately in storing insulin correctly.
What expires while nobody is looking
Ketone strips are the standout, and the reason is structural: you need them least often, so you check them least often, and you reach for them on the one evening when being without them actually matters. They also have a shorter life than people assume, and some have their own limit once the pot has been opened, which is a second date on top of the printed one.
Glucagon is the other one, and for the same reason. It sits in a drawer for years, and the moment it is needed is the worst possible moment to discover the date. It is worth a specific, scheduled check rather than trusting that someone would have noticed, and worth knowing that the people who might have to use it should know where it is and that it is current.
Then the rest: test strips, which can carry a limit once the pot is open, sensors, and hypo treatments, which do expire and which also have a way of being eaten and not replaced. Putting the whole lot in one visible place rather than spread across three drawers is what makes an audit possible at all.
One habit, one calendar reminder, and ordering early
The habit is new behind old. When supplies arrive, they go at the back and the existing stock stays at the front. It takes a few seconds at the point of unpacking, it is the whole of stock rotation, and without it the newest box ends up at the front and the oldest quietly ages out behind it.
The calendar reminder is the other half. Twice a year, look at everything with a date on it, and replace what is close. Pairing it with something you already do, such as a clock change or a repeat prescription, means it actually happens. Anything expired goes back to a pharmacy rather than in the bin, and sharps go in the sharps bin regardless of whether they were ever used.
And order before you are low rather than when you run out. Prescriptions take time, bank holidays stack up, and supply problems with a particular product are not rare. Holding a sensible buffer is the difference between an inconvenience and a genuine problem, and if you are ever close to running out, telling your team early gives them room to help rather than none.
What changes how much this matters
The in-use period differs between insulins, so knowing the number for yours is worth a minute with the leaflet. How you get prescriptions matters more than people expect, since a monthly delivery leaves less slack than a three-month one. And a shared kitchen at university is worth a labelled box, so nothing gets moved and nothing goes missing.
Where this goes wrong
Examples, not instructions or doses.
In use for far longer than its room-temperature life and looking completely normal throughout. A marker pen answers this in two seconds.
Reached for during an illness and two years out of date. The item you need least often is the one most likely to have expired.
Fresh supplies stacked in front of the old ones, so the oldest ages out at the back. New behind old removes the whole problem.