Too Much of a Good Thing, AKA Hoarding & Expiration Dates

So I am very organized in storing my insulin pens, insulin vials, CGM supplies, and pods oldest to newest. My prescriptions are written to give me padding for problems that inevitably arise which eat through supplies unnecessarily early.

I like having extra supplies stockpiled, but I think it has caused me some issues in the last few months.

Pods expire 18 months from the date of manufacture. I have personally noticed a much higher failure rate as my stockpile gets older. Pods with 3 months left before expiration have been failing more frequently than newer pods. For 2021, I did not have any pod failures until July. I had 1 or 2 pod failures per month until November, when I had 5 pod failures. Of course it could be a specific Lot of them with issues, but I am really leaning toward the age and expiration date. I have to get my pods through a supplier so there’s no telling how well they are stored at the supplier…or how well they are maintained during transport to and from the supplier. After another 2 failures this month, I’ve jumped ahead to pods that don’t expire until next September. Hopefully those will work better.

As far as insulin goes, I cannot tell how far out the expiration date is from the date of manufacture…but I’m guessing 2 years based on the expiration dates from the newest insulin fills I’ve just gotten. I inject via pen for my meals and corrections, and I was using a pen that expired that same month. I’ve read that insulin lasts way longer than the expiration date but I’m not convinced of that now. For the last month or two, my injections have been terribly sluggish and ineffective. Probably only 60% efficacy? So I switched to my newest pens and my injections are acting right as rain again. I have also started using my newest vial (the one I was on expires in five months) and it seems more effective, too. My time in range is definitely better.

It bothers me that none of these items were actually past their posted expiration dates. And you never can conclude anything with 100% certainty in T1D, but it seems more likely than not that the fresher, the better with pods, vials and pens. I was ready to pull my hair out with the unresponsiveness of my body to what I was injecting. I hate putting in more and more and more and wondering if it will all finally kick in and tank me. But I am grateful that what I am currently doing is behaving as planned. I like living and eating. Both good things. :slight_smile:


In broad terms so far as diabetic supplies are concerned I have had problems with things which have batteries but haven’t with other stuff. GE and (pure) human insulins shouldn’t have a problem unless they get hot. They are stable to 70C. Insulins which use zinc are slightly different, though apparently more stable to temperature. Stability to chemicals is a whole different matter, but that shouldn’t happen in storage.

Tests in real world environments show that insulin remains completely effective over a 4 week period with temperatures up to 37C; i.e. body temperature.

The problem here is that momentary lapses in storage conditions will destroy insulin very rapidly - seconds, not hours. In my experience it is difficult to avoid these conditions; direct exposure to sunlight might not heat the whole vial or pen up, but localized temperatures alone might be enough to damage the insulin structure. I also haven’t seen any studies on the effects of UV but my chemistry background tells me it is likely to be highly destructive. So if something seems to start going wrong with an in-use pen or vial I would always throw it out; I might be wrong but at least I’ve factored out one of the potential causes of sticky highs.

There’s a simple catch phrase; If in doubt, throw it out.

Batteries, however, are a disaster area; they just degrade over time and the rate at which they degrade depends to a large extent on the quality of the manufacturing process. It should always be possible to find out when a pod or g6 transmitter was manufactured and when it will ‘expire’; it’s printed on the carton. (It’s not on the device itself; the manufacturer can decode the serial number but I don’t think any of us can.) The problem here is that the batteries in the pod or transmitter were manufactured before that date and we can’t find out when!

Personally I think that both Insulet and Dexcom need to acknowledge this and stop printing BS on the cartons; rather they should print the original manufacture date of the batteries and work from that.

To make this worse my experience as a Dexcom user in the US is that the US supply chains to the pharmacy which supplies my transmitters are a total joke. I’ve received transmitters and sensors out-of-order. The same applies to insulin, but I worry less about that.

To make worse badder Dexcom have explicitly told me to ignore the use-by date because I must use the transmitters in the order received. And I must use them within 150 days. I interpret this as a consequence of the battery life issue; if they used the battery manufacture date this foolish situation would most likely not exist.

Anyway, the 150 day limit ends up meaning I have an argument with my wife (who is desperate not to run out of my supplies) about refilling the transmitter prescription. The 150 day demarcation along with the very tight control Dexcom exercise over transmitter life means that if I get an order only a few days in advance I will be out of transmitters if one fails…

Batteries are bad news.


This is why you rock!

And this thread reminded me to check/rotate my supplies. As with @jbowler, the spouse always wants me to have like 10x more than I need…


I use insulin that “expired” up to 4 years ago :grimacing: works fine for me. Vials. Idk about pens. But yeah expired pods tend to fail more in my experience so far.


I’ve used expired pods with no issue.



I expect that all of us develop a bit of the T1D hoarding gene and have to battle expiration dates.

I think that I now have 8 of the old two-part U-mix glucagon kits. All of them badly expired. One in the car, one in the fridge, one in suitcase, one in carry on, etc. If I ever need it, I hope it still works …

However, I agree with @jbowler that batteries scare me the most. In my case, Dexcom G6 transmitter batteries. In many respects I liked tge old G5 transmitter that came in a box with a little magnet that didn’t connect the battery until you pulled it out of the box.

While my insulin stockpile isn’t great enough to worry about expiration, I do at least worry about it going bad because of temperature. My in-use and on-deck vials are not refrigerated, but I also struggle to differentiate “weak” insulin from a poor absorption infusion set location. After nearly 50 years, most of them with MDI, I fear that I’ve got significant scar tissue on my belly.

I would wager that we have some real champs in our midst when it comes to hoarding supplies and having backups for backups.

Happy Holidays!



Everyone has to do what works for them. I certainly find it reasonable to believe that in general, fresher insulin and fresher supplies will be prone to fewer hiccups than older insulin and older supplies. If you can stockpile forever and it works without issue for you, awesome! That would be my goal. But that’s not currently turning out to be a great strategy for my BG management so I need to adjust accordingly. And I am.

I think it’s an interesting set of questions that I certainly don’t have an answer to:

When does insulin lose efficacy and what does that decline look like? Gradual degradation? Sudden drop off in degradation? How would you be able to tell? What things matter in insulin storage and what things don’t matter (i.e. temperature, light, etc)?

If we get used to using older insulin in our stockpiles, would we mentally adjust to needing to dose more and more gradually as it putters out and not notice that gradual change associated with the waning efficacy?

Does anyone run a tight enough dietary/insulin/activity routine to accurately compare two year old insulin (or older) to fresh insulin?


The thing with insulin is that it seems to be surrounded by an awful lot of “always” and “nevers” and people are really set in what they believe about it. I just want to be careful to take the most reasonable approach to troubleshooting in my own care.

I had discussed on this forum in early 2019 that my Dexcom transmitters nearing the end of their life gave really, really wonky results. It was explained to me that it couldn’t be the transmitter. That it had to be the sensors, or one of a million other things, but definitely not the transmitter because this is not how it works.

The issue came up again this year and now there seems to be more support for the notion that transmitters can act screwy near the end of their life. Dexcom tells people that. My Dexcom reading issues both got straightened out with a new transmitter each time I posted about it. Even using sensors from the same batch with the older and newer transmitter.

I’m only pointing that out because we all know to take what the medical community tells us with a MASSIVE grain of salt. We’d never survive if we listened to them, lol! But I also need to be careful in what I believe from others’ conclusions, even on FUD, because we all have different experiences and needs and variables…and it is pretty hard to isolate variables in diabetes care.

Maybe insulin never goes bad. I would love that. But I also don’t think there’s anything wrong with questioning it.


I’ve found that “always” and “never” are rarely always or never; there are “usually” exceptions or mis-understandings to almost every “rule”. That said, we often find something hasn’t worked for us “yet” or has worked for us “until” and then the exception occurs. But “fresh” seems to be a good thing most of the time or until fresh isn’t available.



I think that you are wise to consider the stability and activity of insulin over time and temperature.

I thought to myself: “Surely science folks have looked at this?” so I asked Ms Google what she knew about “thermal insulin degradation”. One interesting article she provided is listed below.

Note: this link does not have a paywall, but DOES ask about cookie settings. I won’t pretend to tell others how to respond but believe that this is a legitimate link …

Note: while I am an engineer (retired) by training, I don’t know bupkis about biochemistry, insulin structure, etc. I’m hopeful that some of the better-schooled members of our community will read this an comment.

The premise of this study is, I think, interesting: If you are a T1D in Kenya with no access to refrigeration, what happens to your insulin on a shelf over it’s 4-week usage lifetime?

They used a small temperature data logger sitting next to the vial of insulin and learned that the vial cycled from a minimum temperature of 25 C (77 F) to 37 C (98.6 F) on a daily basis.

They then went back to the lab and programmed a furnace to mimic that daily cycle and put different vials of insulin in there for periods of 4 weeks and 12 weeks, then used a bunch of tools that I don’t fully understand to determine how active the insulin still was.

There are lots of details here, by my reading is that after 4 weeks of this temperature cycling, insulin hardly degrades at all, and after 12 weeks of this, it only degrades a bit. But, that is only my reading … to be taken with @T1Allison’s MASSIVE grain of salt.

Note: this article doesn’t talk about expiration dates, but, to me, sheds some interesting light on the question of thermal degradation of insulin.

I hope that this adds modestly to this discussion. Note: I make no representation that this is the best possible article on this topic … there may be better sources.

Happy Holidays!



I’ve got a first degree in biochemistry and chemistry. I read a different version of that primary source you quoted before my previous comment. The source is extremely disturbing, for reasons that I hope everyone realizes; neither the version I read nor that version hide it.

I generally accept the results; the method might chill me to my heart, but the results are no doubt correct.

They are also imprecise and not very useful. They don’t contribute much to this discussion, beyond the fact that I previously stated about storing insulin at blood temperature for four weeks and that has little use.

With my chemist hat on I stand by my original statement; below 70 is safe. (“70” is to one decimal place - 65 - 75.) The issues posed temperature versus radiation are very different; temperature (biochemist now) is a deadly thing destructive to everything, radiation happens in steps, quanta some say, and is therefore gradual.

The fact that we have subjected people to the conditions in refugee camps is just something we will all have to die with.

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Thank you, everyone, for your thoughtful replies. I always appreciate dialogue and collaboration!

I’m looking through articles and thought this one was limited but interesting:

Back in 2013, I was using CVS because my insurance company was having a ■■■■■■■ contest with Walgreens so I was forced to move. Then I found out that CVS would fill my pen prescriptions and leave them sitting out all day long on the counter (I was told it could easily be 10 hours if they’re busy that day) from the time the tech filled the prescription until the time the pharmacist actually got around to signing it off or whatever they do. Now, maybe that does not actually matter because an air conditioned pharmacy is not an extreme environment. But I did call around to five other CVS pharmacies in my area and asked their protocol for insulin handling. I found one CVS whose pharmacist was hardcore that insulin was only allowed to sit out for 10 minutes before it had to be returned to the fridge. And the rest said it would usually sit out several hours before going back in the fridge.

My main issues with this are (1) lack of standardization and (2) this contradicts the handling instructions that I understand insulin comes with. We’re told that once it comes to room temp or is opened, you have 28 days. So sitting out all day at a pharmacy would contradict that rule.

Anyway, none of that may functionally matter but it raises my eyebrow, at least.


Well…if it’s just your eyebrow…. Seriously, thanks for the research and references; it sheds light for us all on the issues. While informal tests of various folks here on FUD and elsewhere indicate insulin may be less susceptible to temperature impacts than we’re led to believe, I’m sure most try to follow the guidelines for storage and maintenance. Supply-line security is almost unaffordable, if not impossible, whether inside or outside the US…as your own experience indicates. And that’s for the routine “aspirin”, let along a critical drug.


I’ve been hanging around @Eric too long and found myself in my garage disassembling an expired Novolog pen to see how it’s put together and how the insulin is stored more clearly.

I’m still operating on my personal theory that there’s something about disposable pens that makes them more prone to insulin not lasting forever in them as opposed to vials. And maybe it’s the handling they receive through the pharmacy chain since they’re seen as disposable and less vital than vials? Strictly an immature theory and not one that I’m totally invested in. But I personally am going to be more careful with age of insulin pens because I’m seeing night and day difference as to efficacy and insulin action time with my newest pen compared to my oldest (which was at end of shelf life).

To each their own! But I’m just sharing my current operating theory for myself!


What about the effects of leaving a pen needle attached? I always do.

I pull a new pen out of the fridge, attach a pen needle when it’s cold, and leave it on for a day. I switch pen needles once per day and use each needle for about nine injections. The pen lives in my purse until I use it all up. I go through a pen about every 10 days.

This is probably a stretch for what could lead to insulin pen efficacy issues…but I like theoretical discussions so here I am. :rofl::woman_shrugging:


:joy: :joy: :joy:


Besides the contraptions built around the vial to assist in proper dosing (all the blue and orange areas of the pen), the vial is pretty much like a standard vial, though, isn’t it? It looks like it…a glass tube with an area at the top for putting the needle through.

We use the Novolog Flex pens as well for Liam, but we never use the needle caps with the pen…we use the needle that comes with each omnipod and just take it out with that and dispose of each one as we use it. I use very old insulin with Liam this way and I never see insulin resistance issues in him. I used to sort the insulin by age (oldest on top, newest on the bottom), but after you have a stash my size, it gets VERY difficult to sort them so I just kind of shove the new toward the bottom and try my best to push the old stuff up some…but it’s definitely not an exact science. The pen we are on now expired October of 2020 and it’s working just fine. :laughing:


So do you lean toward the efficacy issue I’m seeing being more of a one-off than anything else?


Or maybe it does have to do with the pen caps somehow…those pen caps, if they stay on top have a puncture constantly in the rubber and perhaps that’s somehow allowing some air in or something that’s eating away at the efficacy over time?

Only spitballing here…no idea if that’s true, possible, or the case. Just thinking out loud.


I imagine it’s a difference of the pen or needle type, but I couldn’t get the pen cap (Novolog FlexPen) back on with the needle attached. I have BD Nano 2nd Gen 32g 4mm needles; a small ridge at the base prevents the pen cap going on. Please, make my day and tell me how to get around that…I probably gave up to easily.