Cartridge vs Vial

What is the difference between insulin cartridges and insulin vials? I use a pump but my dr called in a new prescription to my pharmacy for insulin cartridge, not my regular insulin vial prescription. Can I use cartridges with my pump?

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Cartridges are designed to use with reusable insulin pens. Each cartridge hold 3 mL or 300 units. Five cartridges come in each pack, for a total of 15 mL or 1500 units.

A vial holds 10 mL or 1000 units.

You can use cartridges to fill your pump. Since cartridges have a rubber stopper at the end that can move up and down, there is no need to inject air first. I also prefer using cartridges because I feel like I get fewer air bubbles in my pump cartridge, and I also always keep a backup pen around to use the cartridges in should something ever happen to my pump.


Thank you, @Jen, for your help! I just spoke to the pharmacist on the phone and he recommended switching the prescription back to vials as he said it is a bit difficult to remove the insulin from the cartridge with a syringe. So that is what I did.

After seeing your response though, I think I’d rather use cartridges if it creates less air bubbles, something I’m always getting, and still able to remove the insulin via syringe! I will try them next refill.

Which pump do you have? For Medtronic minimed pump, the reservoir filling process uses a connector to make it easy to get insulin direct from vial, no air.
Not sure how you would fill using syringe or pen cartridge, without getting more air in it.

I use omnipod. It comes with its own syringe which I use to transfer the insulin from the vial to the pod.

You definitely still get air bubbles. I just feel like it’s less, since you don’t purposefully inject air into the cartridge before withdrawing.

I believe even with Medtronic, if you’re using a vial, you need to inject air to equal the number of units you want to withdraw, no? This is the part you can skip with a cartridge. Cartridges still get air bubbles, for sure, I just feel like it’s less than with a vial. (Though keep in mind I’ve used maybe one vial to fill my pump in the past 12 years…)

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You can also do this with the cartridges. We moved from vials to cartridges because I understand from the FUD community that you get more insulin by asking for cartridges. But you can use the syringe in the POD to extract insulin from the cartridges as well.


I have no idea how things work in the US, but in Canada cartridges come with 1500 units (five cartridges per box) versus 1000 units, but the cartridges cost more. So in the end, I think you pay the same per unit of insulin.

FlexPens offer 50% more insulin with each prescription for us (1,500 units in a box of 5 pens, compared to 1,000 units in a vial), and the co-pay for us is the same (zero, with the Novolog card).

Oh, that is good to know that the Omnipod syringe can be used to extract the insulin from the cartridge. I was wondering about this. They seem a bit more handy, too, than the vial since you could actually use it w/ a pen for an emergency injection if the pod fails.

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Having cartridges around also provides the added benefit of going MDI in emergencies. Just slap a pen cap onto the flexpen, dial in the units, and press.

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I think it is the same in the US. At least that is what the pharmacist told me last night on the phone. Vials and cartridges cost the same except I think you end up getting 5 units less with the cartridges when ordering 5 vials. At least that is what they told me.

Ah, yes, that is what I was thinking, too!

I don’t quite remember the full conversation we had previously, and now I can’t find it…but I seem to remember the concensus being that cartridges > vials if for no other reason that you have a fast and easy way to admister MDI in the even of a failure, emergency, etc., If someone remembers the past conversations and can link it that would be great!

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Yes, I can see that being an important advantage, too, as Omnipods fail from time to time. I currently carry a syringe with me in the event a pod fails. Next refill I will give cartridges a try.:slight_smile:

Yes, this is the reason I use cartridges.

But as far as saving money, for me it works out to about the same, if not being a bit more expensive, to buy cartridges.


I think @Michel uses the cartridge with a “pen needle” tip to inject directly into the OmniPod. I haven’t tried this.

I do get the cartridges/PenFills of Novolog and use the Omnipod filling syringe to fill them. It’s tad but fussy. And once we spaced and injected air and blew off the rubber end cap. But, if you are paying attention it is very easy to use the Omnipod syringe to fill from a cartridge.

I take the cap off of the Omnipod provided syringe, place it gently on top of the rubber stopper of the cartridge and grip that in my left hand, left thumb on top of the Omnipod cap on top of the rubber stopper. Then I use my right hand to place the needle into the cartridge dispenser area to withdraw the insulin. I find that it is easiest if I have moved the plunger up and down a few times in the syringe prior to using it. Also I apply gentle pressure with my left thumb on the cap to depress the rubber stopper in the cartridge.

It works a charm!

And I’m bad at math but once did attempt to figure out which was cheaper - cartridges vs. vials. We went with cartridges. Also they’re smaller so if they get lost or dropped or broken we are out less insulin.


Can you document or video this process? Sounds intriguing but following it mentally was difficult.

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I believe the price is very slightly higher for cartridges per unit, but really not noticeably.

Yes, we do fill our pods from cartridges. The additional benefit is that we always carry a refillable pen, which uses cartridges, as a backup, or to inject large amounts, so it is really useful to have cartridges do double duty!


A ny advantage to using the cap to depress the rubber stopper versus just pulling back on the plunger of the pump cartridge? I’ve always just done the latter and pulled back on the plunger of the pump cartridge. (I’ve also always moved the plunger up and down the pump cartridge several times before actually filling it—this is just the way I was taught to fill cartridges with my Cozmo as there was a lubricant inside and moving the plunger up and down and twisting it a bit as you did so helped disperse the lubricant and lubricate the inside of cartridge so the plunger would move easily; not sure if Animas and others are the same, but I’ve just continued to do it.)