[2026 update] 0.3 mL versus 0.5 mL versus 1 mL barrels: resolution matters posts 31–60
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1 · go to the accepted answer.
Narrowing post #29, because the general version has more than one answer.
Two sentences on 0.3 ml versus 0.5 ml and then I will stop, because the rest is speculation and the thread is better without mine.
What is documented is narrow. What is inferred from it is broad. The gap between them is where every argument here lives.
A definition problem is doing most of the work in this 0.3 ml versus 0.5 ml discussion. Once the term is pinned down I suspect the disagreement mostly goes away and what is left is small.
U-100 means the barrel is graduated for a solution containing one hundred units of insulin per millilitre. For anything that is not insulin, the units are simply hundredths of a millilitre.
Noting that the question and the thing people usually mean by it are different.
The arithmetic in post #33 is right; the assumption feeding it is the part to check.
What I would check first on 0.3 ml versus 0.5 ml is whether the thing being measured moved or whether the way of measuring it moved. Those look identical in a graph.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
Not a strong opinion, just a consistent one.
The documentation on 0.3 ml versus 0.5 ml is better than this thread and I say that as someone who has posted in the thread.
I would call the community position on 0.3 ml versus 0.5 ml likely rather than established, and I would be comfortable defending that hedge.
Picking up post #42: that is the part I would want checked first.
One more thing on 0.3 ml versus 0.5 ml that took me far too long to see: the two figures people quote are not measuring the same quantity. Once you notice that, the apparent contradiction disappears.
On post #40 — agreed on the reasoning, with one qualification.
U-100 means the barrel is graduated for a solution containing one hundred units of insulin per millilitre. For anything that is not insulin, the units are simply hundredths of a millilitre.
I have seen it go both ways, which is why I hedge.
Thank you for taking the time. That was more work than a reply usually is.
Genuine question rather than a rhetorical one: has anyone here actually observed 0.3 ml versus 0.5 ml, as opposed to read about it? The thread is long and I cannot tell.
Post #46 answers the question as asked. The question underneath it is different.
A methods point on 0.3 ml versus 0.5 ml rather than a substantive one: if the comparison is not like for like, the difference you are measuring is the difference in method.
Collapsed as off-topic by two members at trust level 3 or above
I read post #48 twice before replying, because I had assumed the opposite.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
Worth saying I have only my own numbers here, and n is small.
Barrel size determines resolution and nothing else. A 0.3 mL barrel and a 1 mL barrel deliver the same volume equally well; the smaller one lets you see what you are delivering.
This follows post #51 rather than contradicting it.
An observation about 0.3 ml versus 0.5 ml that I cannot explain and am posting anyway, on the principle that unexplained observations are more useful public than private.
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That matches what I have seen, for whatever a single anecdote is worth.
On post #56 — agreed on the reasoning, with one qualification.
Adding what did not work for me on 0.3 ml versus 0.5 ml, since the failures never get written up and they are half the useful information.
Picking up post #56: that is the part I would want checked first.
Fixed versus detachable needles: insulin syringes usually have fixed needles (no dead volume loss to the hub). Luer-lock syringes use detachable needles (more dead volume). Fixed needles are preferred for small doses.
Same conclusion as the reply above, reached differently, which is mildly reassuring.
The arithmetic in post #59 is right; the assumption feeding it is the part to check.
U-100 means the barrel is graduated for a solution containing one hundred units of insulin per millilitre. For anything that is not insulin, the units are simply hundredths of a millilitre.
Take the reasoning and check the arithmetic; I do not always get it right.