Insulin: penfills or vials, and why?

The topic comes up frequently as a side line of many threads, most recently here: How do you use your endocrinologist visit?

This is causing me to wonder: do you prefer using penfills or vials, and why?

As for us: we use penfills, because they are more convenient to carry in portable quantities, and because we can divide them them easily in thermoses, still wrapped in their plastic bubble, which protects them from damage.

An additional reason is that we use refillable pens as adjuncts and as back-up for a pump (for bolus insulin). They are more compact than disposable pens, of course, and, in my opinion, environmentally better.


We use both pretty interchangeably, and I don’t think we have a preference. I will say the penfills are convenient, easy to carry, and allow us to always have backup insulin carried around in my son’s meter case. But the vials are easier to get the needle into the correct spot on the septum, and they last longer. So in our house we use both, and I am glad it isn’t an either or kind of situation.

Penfills for travel, vials for refilling pumps and syringe corrections when at the house.


I use both. I fill pods from the vial, and I mostly use the pen for boluses too large to do by pod, though sometimes I’ll use a syringe and vial for that just to, you know, shake things up a bit.

On a recent trip (for two days) I took a new pen each of Humalog and Lantus, just in case my pod failed and my one backup pod failed, and I also took a Humalog vial just in case of some Hollywood disaster movie scenario, but it turned out to be a lucky move since I was away from home much longer than planned and had to switch over to MDI midway so having more than enough insulin was a relief, and the only thing I needed to pick up while away was more test strips and pen needles, which did not require prescriptions or special language skills.


Vials, but truth be told I’ve never had a prescription for penfills so I don’t know what I’m missing out on. I also don’t typically carry backup insulin on a day-to-day basis. Syringes to pull out of my pump cartridge with in case of an issue, yes, but no extra vial.

My backup pens are of the disposable variety, I did kind of want refillable pens when I got them but I wasn’t so assertive at the time and as I was gearing up to ask for a specific refillable pen my endo didn’t believe in the existence of pens with half-unit dosage… so I was happy to get anything that fit that description :roll_eyes: I haven’t really used them yet so I haven’t bothered to ask again, so I’ll stick with my vials for the moment

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If you happen to vacation in Canada or Mexico or Europe, you can just pick some penfills up without prescription to give them a try. I like the extra my son carries around, because while you can get some out of a Pod that fails, you can’t get any out of a pump that gets stolen…


Good to know, though I don’t forsee any international trips currently haha.
I take extra insulin vials and pens when I travel, on a day-to-day basis I could easily just go back to my apartment for backup insulin


I suspect those diagnosed AFTER availability of pens, are comfortable with both. I learned about insulin pens from other diabetics, never mentioned by endo to this day.

I have filled pump cartridges to bring on trips as backup, and used to fill syringe injections when needed. (In addition to vials).

But that has changed. I now have my first pen, and will try out this week.


You are not that far from being able to take vacations to other countries. Even if you go to grad school. If you go to med school you can just steal your stuff from the pharmacy. No one will suspect the insulin getting stolen they spend too much time counting the dilaudid and other opiates.


We’ll see, I’m a bit of a “starving student” at the moment so it’s hard to envision a time with enough cash for travels haha. If my gig after graduation allows me to afford rent and living expenses without help from my parents I’d take that as a win :sweat_smile:


I am sure your parents would consider that a success as well! Don’t worry it happens pretty quick. A couple of years from now if you choose not to live in one of the most expensive cities in US you can get ahead in short order. Of course you can always choose to work and live in the uber expensive places, and never have enough money. Up to you really…


I only use penfills. Because vials won’t fit in my insulin pen.


I don’t use penfills, so I can’t offer anything there, but I carry a vial daily in my go-bag. I also use a silicone vial cover which has save me considerable sum over the last year or two since somehow the vials like to bungee jump without a cord.

This is the cover I found:
[Insulin Vial Protective Case by VIAL SAFE - Fits all 10mL Brands (2-PACK) - Never Risk Breaking Your Insulin Vial (1 Short, 1 Tall)]


Interesting. At the clinic I go to, the assumption is that people use pens or they pump. Syringes would be viewed as quaintly old-fashioned. When I was on MDI and getting a prescription for a new kind of insulin, the question didn’t even come up – it was automatically written for pens.


I was on nph+reg (syringe) prior to starting pump (with reg), and using pump since then. I used the autojector with NPH, REG injections for many years prior to pump.
I think pens came out after I started pump. So I never did traditional MDI with newer insulins. With pump, I had syringes for backup, but rarely used.

But today, did my very first pen injection!!


And…What did you think? Awesome, anti-climatic…


We just finished the dreaded back-and-forth with the CDE trying to get Novolog PenFills. She had written a prescription for vials despite clear written instructions from us otherwise, and then became frustrated when when we insisted on PenFills. Here was Eric’s reasoning:

Reason #1: The PenFill cartridges provide 50% more insulin for the same price.

Novolog vial is 10mL.

Novolog PenFill cartridges are 3mL and come 5 to a package so 15mL.

They cost the same.

Reason #2: The amount of insulin held in the vial is awkward and leads to waste.

Also, the OmniPod holds 1.5mL, so 1 box of 5 PenFill cartridges will fill 10 OmniPods (each Pod takes 150mL).

1 vial will fill only 6 OmniPods and then I end up with 100mL which isn’t enough to fill an OmniPod.

Reason #3: Less time outside of the fridge for travelers.

Also, because I travel all the time, having insulin in smaller containers is good. Imagine a 1 week trip. With the PenFill cartridges I can take 2 (which is enough for 4 Omnipods - 3 for use and 1 backup). The other 3 can remain safely in the refrigerator. Now, if I have a vial, I have to take TWO of them (one is the primary, and the other is the backup in case the first one is dropped). I’m exposing 12 pods worth of insulin to travel temperature (outside of a fridge).

Imagine a 2-day trip. I could take 2 Penfills (one for use, one for backup). Or I could take 2 Vials (one for use, one for backup). In this case, I’m exposing a LOT of insulin to non-fridge temperatures.

Reason #4: They are glass.

The vials are prone to breaking if dropped. The Penfill cartridges are less likely to break, and even if they do, they contain less insulin so the loss is less painful.

I find the cartridges are less expensive, less risky, and more convenient.


I think he made a good case and we’ve been approved for a year’s worth of PenFills. Yay!


Just to play devil’s advocate, I can use the same reasons, but reach the opposite conclusion.

Reason #1: Cost: I have a prescription for two vials of Levemir (20 ml), but my Tresiba prescription is for five pens (15 ml). But really, comparing out of pocket cost after insurance seems unfair without considering the actual cost of the drug itself which I assume is comparable. I don’t refill a prescription just because I can - I wait until I have only a spare vial or two.

Reason #2: Waste: I use all the insulin in a vial, regardless of how many days since opening. I’ve never found it to lose potency (there are posts here at FUD testing this). And unlike a pen, I can get all the insulin out. To get all the insulin out of a pen cartridge, I need to use a syringe - but then I’m using a syringe anyway so why sometimes bother with a pen?

Reason #3: Fridge: I’ve never bothered with refrigeration on trips and again there are posts here at FUD that back this up as being a non-issue.

Reason #4: Glass: To me being made of glass is a benefit since I’m putting less plastic into the waste stream - two glass vials versus ten plastic pens. In all my many years of injecting I’ve only dropped and broken one vial (tile floor - they don’t break on wood or carpet), so to me not an issue worth worrying about.

In addition syringes are smaller and more portable than pens (I re-use syringes many times), and smaller and more comfortable to hold while injecting. Plus I can do half unit or even smaller fractional amounts using a syringe. I find this useful for Humalog which I happily buy in vials.

So if I could, I would get Tresiba in a vial, but that is not an option so I have been forced to use a pen. But I am interested in whether it is possible to get Tresiba in PenFill cartridges in the US, because my pharmacy told me they could only get the disposable pens? If I could get a PenFill cartridge I could use it with my syringe as a mini-vial. Does anyone get Tresiba in PenFills?

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Ah! Those are some good points too. (I’m fighting both a cold and a headache so my reply is a little limited - I clearly shouldn’t have bragged my health was fine on Friday. :rofl:)

The PenFill things from Novolog are mostly glass and not giant like the disposable pens.

And yes, I agree, we’ve left insulin out for a long time, unrefrigerated, like weeks and weeks, no problems so far. But it does make an excellent excuse for insurance purposes. :slight_smile:

And for your first point, since I am clearly working backwards, we do refill before we run out. Ideally I would like to fill all prescriptions on the same day monthly. Years ago, there was a surprise ending of a job unexpectedly. That sucked. Having spare insulin made that time less bad. Although there’s plenty of workarounds here on FUD, like lower cost insulin regimens and whatnot. But I’m perennially worried about job loss now - and thus an insulin and diabetes supply hoarder.

Always glad to consider both sides. :grinning:


Keep in mind cobra can cover a gap.

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It’s true, but Cobra was SO expensive seeming at the time. Ironically, the biggest charge was for me, as the “spouse” who was insured.

Anyhow, I’m thankful that time is behind us. :slight_smile: