Pen -vs- Syringe precision dosing

Yeah, I’ve realized since starting that it’s probably not accurate (and I only do 1/2u alone at times - the 1/4 is usually added to a unit or two, and I KNOW that’s not at all accurate…playing a guessing game). There have been many times recently I wished I had a pump.

So what’s a person to do when they need small doses but pens or syringes are (currently) the only option? Do as @ClaudnDaye said and just “feed the insulin” to get up to the right carb count for full units from a pen?

Oh - another person in a FB group I’m part of has suggested getting the insulin diluted so as to make it easier to dose smaller. Anyone ever tried that (maybe I should make a new topic for this…)?

I’ve done it. I’ll post a thread on it with some details.

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Shall we split this topic up into syringe cases (the original)
2) pen vs syringe precision dosing
And so on… ?

Your wish is my command.

Pens also apparently cannot measure just a half unit unit. At least the half-unit pens I’ve used (Luxura, JuniorSTAR, and Echo) all state that doses of less than one unit are not accurate, though doses of more than one unit (say a unit and a half) are accurate. So it seems that, regardless of what method you’re using, it’s probably best to dilute insulin if you need doses that small. Which is one reason I love my pump, because I often do find taking half a unit to be useful. I’m wondering how pens are using the same technology as pumps, though, if pumps can measure in increments as small as 0.025 of a unit and pens aren’t even a tenth as accurate…?

They both depress the plunger with a screw type mechanism… which allows a very large motion of the plunger to be mechanically reduced to spit out a tiny amount of insulin at he other end. This allows for a great increase in precision… of course more so with the pump which has much more fine screw mechanism and control mechanism…

It makes sense that a pen would struggle with ultra small doses like half a unit too, because the mechanism (like any mechanism) has some slack in it and it needs enough movement to actually take that slack out of it before the insulin actually starts moving… whereas the pump is being nearly continuously slowly driven by its electric motor keeping all the slack out of the system… this is actually one theoretical advantage of a syringe… it is a solid system, no moving parts (except the solid plunger which directing shoves the insulin right out of the syringe) , no slack… of course that only actually really matters if you could precisely administer small doses with a syringe-- which you can’t-- so it’s really just a theoretical thing

I used Luxura pens for years, and it was either one of those or one of the older HumaPens where I once thought I dialed up and delivered a dose, but only a fraction of the dose was actually delivered. I didn’t realize my meal bolus hadn’t worked until I tested hours later and was 20 mmol/L. I tested the pen by drawing up and injecting into my hand, and even though the pen primed just fine, and the pen could be dialled to the correct amount and the plunger that you press down went down fine, something was broken inside and the actual plunger that pushes against the vial only decreased enough to push out about a unit or two. That’s only ever happened once of the dozens of reusable pens I’ve used in my lifetime.

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Depends on the pen. Our fast-acting (novolog) pens have 1/2 unit measurement capability. The slow-acting (Lantus) pens only have full 1 unit measurements…apparently intentional since it’s rare that you’d take less than a full unit for 24 hours of slow-acting insulin.

We diluted at first, at a ratio of 1:10, because our son needed those small doses. I found it was a little unreliable with the diluent but you can do that if you need. From what I remember you have to either get it at a compounding pharmacy, premixed, or you can get the bottles of diluent from your endo clinic.

Or directly from Eli Lilly or novo Nodisk for free

I’m reading this thread and chuckling. I’ve used the same Novopen with cartridges for about the past four or five years. I’ve had zero problems with it nor have I had dosing errors.

Of course it helps that I have insulin resistance and rarely ever take a bolus of less than ten units. So one drop of insulin either way wouldn’t really effect me :wink:

Unless it’s a huge error, we never really know. With either pen or syringe, once it’s been injected, there is no way to tell if there was a small difference in the amount given compared to the intended dose.

It would be cool to have a gravimetric scale and test the theory of which is better.

Hi Sam, I am new to this forum but definetly interested in diluting my Insulin. I have been using NovoRapid Echo pen since years but being very sensitive to insuline I am thinking to dilute it and see if BG management improves further. Who did you get in contact with at Novorapid to get diluent? Did you specifically mention something?
Many thanks and thanks also for the forum which after one hour reading already gave me this sexy idea! :grin:


I got it from Lilly for free. It’s basically the same, it can work in any insulin.


Thank you Eric!!! I will try and let you know, I have some doubts on the diluting method and accuracy so I guess I will have to do some experiments. But this could actually solve a lot of problems I have, at the moment my sensitivity is so high that I need only 1 ui for 25cho.

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When doing MDI, I used the heck out of it. I can tell you that for me, diluting with a pen and using it for small corrections was huge. Why should pump users be the only ones that can do a 0.10 unit dose?!

Try it and let us know!

Not sure if you have seen this, but here is one way to empty the pen and fill it with whatever you want. I like the Lilly pens and cartridges for this, but I am sure you can do the same with Novo pens.


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Let us know how it goes. I wouldn’t be terribly concerned about the diluting precision as it becomes less and less consequential with dilution as long as you’re grasping the concept of what the desired solution ~should~ contain … eg the difference in .18 and .22 is much smaller than the difference between 1.8 and 2.2, or 18 and 22

BlockquoteNot sure if you have seen this, but here is one way to empty the pen and fill it with whatever you want. I like the Lilly pens and cartridges for this, but I am sure you can do the same with Novo pens.

Yes, I refill my novopen cartridges the same as humalong cartridges are refilled.
And I also use Novolin R for a couple of specific daily doses, dispensed from a Humapen HD.
You CANNOT refill a Novopen disposable, as the dosing mechanism can’t be dialed backwards on those like the Humalog and Basaglar pens can.

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That is enough of a reason for me to stick with the Humalog pens.

My new “go-to” pen for any occasion is the Humalog KwikPen Junior. It really has all the best features:

  • It’s more compact than the non-disposable
  • It’s refillable
  • And it has 1/2 unit doses.

The fact that they finally are making a small1/2 unit disposable is great! It’s a perfect pen.