Pen -vs- Syringe precision dosing

I’ve seen studies show that pens are actually more accurate than syringes… dont know how valid that is but it’s what the research I’ve read says… can’t find the study at the moment

I’d be interested to see that study. One thing that always annoyed me about pens is that you have to hold them in for ten seconds to make sure the full dose is delivered. When I first used pens at age 16, I spent a week away at summer camp and my blood sugar was insanely high the entire time because I wasn’t holding the pens in for those ten seconds. Even when I do hold it in, often there’s still a drop of insulin that comes out after I remove it. I don’t ever remember these issues with syringes—no drops of insulin even if you inject really quickly and remove the needle right away. I’ve also heard that the first 1/2 unit marking on a pen is not accurate (it can measure 1 1/2 units or more accurately, but not just 1/2 a unit). So if someone is wanting to inject 1/2 a unit or 1/4 of a unit, syringes are more accurate. I much prefer pens, though, since I can actually use them and can’t measure into syringes. (Actually I prefer a pump!)


I’d theorize that this is because the pen isn’t actually empty but the syringe is, and that drawing it out of your skin pulls a little vacuum into it which sucks a tiny drop of insulin out of the pen and likely wouldn’t have any effect on actual delivered dose… just a theory though

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Keep in mind, those studies depend greatly on who is using them!

For a drunk monkey, a pen is probably more accurate.


I would pretty much guarantee that pens are more accurate than syringes. It only makes sense…pens “click” to stop at EXACTLY X units so you always know you’re gettting X; whereas with syringes, it’s all about eyeballing it so the accuracy is totally dependent upon how good (or bad) your eyesight and judgement are.

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Early in my TUD days I was convinced that syringes must be more accurate than pens and posted some questions about the subject… someone replied with some legit looking study links showing the opposite to be true…

I would like to see the study. It could really depend on how they are doing it. Like I said, did they use drunk monkeys, or research scientists in the infectious disease lab of the CDC?

How accurate something is depends very much on the person using the tool.

But…syringes are used once, whereas pens are used over and over. So the components that “click” could become worn out over time. The gears wear down, so they don’t click in the same physical position the 1st time compared to the 1000th time (speaking of the pens that are not disposable, particularly).

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****ing hilarious.

Unfortunately so true…

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I can’t read it very thoroughly right now but here’s a starting point

But you can be wrong 100% of the time when using a syringe (eyeballing) versus the EVENTUAL inaccuracy that MAY occur with a Pen.

I suppose this is possible-- but they’re also using a much more precise micrometer type plunger mechanism (same as an insulin pump) whereas the strait in/ strait out plunger of a syringe is inherently vastly more crude even in the most skilled hands… a good analogy would be a carpenter measuring precisely with a tape measure vs a machinist measuring precisely with a micrometer

Even the most skilled carpenter with the top of the line tape measure can’t measure anywhere near as accurately as a novice machinist with a cheap micrometer from harbor freight

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I couple of other things to consider though.

On some pens, you can draw up a number, and if there is not enough insulin in the cartridge, it will give you what it has and then stop. You have to look at the number it stopped on, and then load a new cartridge and then add the amount that was not given. That process is prone to errors.

If you leave a needle in a pen and re-use it, that can also cause problems. With Levemir, when I use a needle that has stayed on the pen but not been used for more than a day, it will clog up. I have to prime the hell out of it. I can draw units and press the button and it will depress all the way, but no insulin will come out. After a few times of priming, it will all squirt out, all the priming units at once. I have only noticed this with Levemir, but if I had not noticed it, it could have really screwed me up. And BTW, with Levemir, it does it every single time a needle stays on the pen for more than a day. This is another issue that the syringe would not have.

With pens, you are looking at the number wheel, which can also become a bit off-center after enough use. I have notices this with some disposables. You can look at it, and think, “Is the marker on 5 or 6? It’s kind of right between them…” Again, a problem with re-use.

A vial of NPH can have sediment form on one side if it has been sitting still for months. With a vial, it is pretty easy to see. You can roll the vial and mix it back up. With a pen, you may not see the sediment form, particularity if it is on the tip (needle side) of the pen.

I just bring those topics up because none of the above scenarios were a part of the study. And those are all legitimate real-world scenarios that can be considered.

On a side note, the study you referenced was interesting in that syringes had a tendency to overdose, while pens tended to underdose.

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On all of the pens I’ve used, all disposables, you cant select a dose any higher than what’s left inside the pen… sure if you have to take multiple injections with either a pen or a syringe you are increasing your margin of error each time

Sure there are specific pros and cons to each method and if you’re using a malfunctioning pen it can’t be expected to perform any better than a malfunctioning syringe or malfunctioning pump for that matter-- but I would suggest that the assumption that pens are inherently less accurate than syringes with a skilled user is not valid…


Human error is far greater than computer error, in general. And most computer error is a result of human error. If I am not paying attention and stop the pen between clicks, that’s on me…not the pen. Our pens that we’ve used are clearly numbered and have distinct clicks each time we get to where we want to stop.

Especially for toddlers, syringes are NOT at all practical for shots. Not only are the syringe needles very thick and hurt him like hell, but the measuring of insulin in them isn’t ever easy…I remember going back and forth with Erin for every shot we’ve ever had to give him. The measurement lines are so close between each other and not practical to measure (for toddlers)…maybe adults it’s much easier since you’re probably dealing in full unit measurements, not 1/8 or 1/16 measurement attempts. Pens take all the guess work out. Although we now are on POD, we’d never use syringe for Liam if we had the Pen option - ever.


On the Luxura pen (Lilly brand, reusable) you can draw past what’s left in the cartridge.
But either having the pen designed that way, or the way you describe, people have to do the math, which can potentially mess some people up.

That isn’t actually what I was arguing. I was not saying syringes were necessarily more accurate. But what I was saying, is that if you used stooges in your experiment, it would be much easier to show pens being better than syringes. My point is that a syringe is more likely to be a huge mess-up with a clown using it compared to a pen. But when competent people use both, they are much closer. I am not necessarily saying one is better than the other. They both have potential problems. I was just highlighting the pen problems for the sake of discussion.

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One measurement when a vial is nearly empty still beats measurements for every single shot, every time as with the syringe.

I would never argue that syringes are easier! No doubt pens are tops there.

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Same. :grimacing: When my toddler knocked my vial off the coffee table onto the tile floor (yes, I shouldn’t have left it there…), a kind fellow t1 sent me a couple pens to tide me over, which I’m still using now, but with syringes, because I didn’t feel like it could possibly be accurate at just giving me 1 unit. Of course, I’m still dosing in 1/4-1/2 unit increments at times, so syringes became necessary.

But pens don’t dose in that small an increment, right (asking genuinely out of curiosity)? My I:CR is 1:35 most of the day, so a lot of the time I only need 1/2 unit for snacks, or sometimes my meals will be something like 1.25-1.75 units (usually when I have to split my bolus for fattier meals), which is why I’m still using syringes, because it’s easier, in a way, to just dose what I need rather than eat (or don’t eat) the extra 10-15 carbs all the time to bump things up or down to an even unit.

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That’s correct, which is why we had to switch to a pump so that we could ensure small doses (.05). But of the two other alternative methods…the one we would use would have been (and was) pen. We just “fed the insulin” in those days since we couldn’t really dose as small as we needed too.

Ironically… with small doses, syringes can’t even accurately administer 1u when administered by a professional nurse… so if you think you’re accurately giving yourself 1/4 to 1/2u with a syringe… it’s highly unlikely… syringes are the least accurate delivery method for small doses