[2026 update] 0.3 mL versus 0.5 mL versus 1 mL barrels: resolution matters posts 91–120
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.
This follows post #91 rather than contradicting it.
A detachable luer needle plus hub can retain enough volume to matter. Whether it matters to you depends on your dose, and the arithmetic is worth doing once.
Adding it in case it saves somebody the afternoon it cost me.
Marking my uncertainty on 0.3 ml versus 0.5 ml explicitly. I am confident about the direction, much less confident about the size, and not confident at all that it generalises past the case in the first post.
The reason 0.3 ml versus 0.5 ml keeps being re-asked is that the answer is conditional and people quote it without the condition. It is not that the answer is unknown.
Taking post #95 at face value and following it one step further.
Two people in this thread mean different things by 0.3 ml versus 0.5 ml and are disagreeing about the definition while believing they are disagreeing about the facts. Worth pausing to define it.
I read post #95 twice before replying, because I had assumed the opposite.
The version of 0.3 ml versus 0.5 ml that circulates here is a simplification of a simplification. It is not wrong, but it has lost the conditions under which it holds, and those conditions are where the interesting cases live.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
Nobody has said the unglamorous part of 0.3 ml versus 0.5 ml yet, so: most of the variation is explained by things that are boring to write about and easy 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.
That holds under the stated conditions and I have stated them.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
I am aware this is the third time this month I have made this point.
Graduation spacing is worth checking before you buy rather than after. Some 1 mL barrels are marked every two units and some every one, and that changes what doses you can read.
Reporting the observation and leaving the explanation open deliberately.
I read post #103 twice before replying, because I had assumed the opposite.
Reading the barrel at eye level matters more than any equipment choice. Parallax at a shallow angle is enough to shift a reading by a graduation.
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.
The evidence for this is thinner than the way I have phrased it suggests.
Two claims get bundled together under 0.3 ml versus 0.5 ml and they need separating. The descriptive one — this is what was observed — is usually well supported. The causal one — this is why — usually is not.
Almost every disagreement in threads like this one dissolves once you say which of the two you are making.
Trying to state the 0.3 ml versus 0.5 ml position in a way that someone who disagrees would recognise as fair, because I do not think the version in this thread passes that test.
Collapsed as off-topic by two members at trust level 3 or above
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 would want the raw data before agreeing with my own summary of it.
Following this. I have the same question and no better information than the first post.
Post #110 is right about the mechanism and I think understates the practical bit.
The question underneath 0.3 ml versus 0.5 ml is usually "how would I tell?" rather than "what is true?", and that one has a method attached to it.
Write down what you would expect to see under each hypothesis before you collect anything. If they predict the same observation, collecting it will not help.
Coming back to post #113, because the follow-up matters more than the original answer.
Syringe barrel size: common sizes are 0.3 mL, 0.5 mL, and 1.0 mL. Smaller barrels are more legible for small doses. Larger barrels hold larger volumes. Choose based on your dose.
Small correction to my own earlier position on 0.3 ml versus 0.5 ml. I had the units the wrong way round, which changes the conclusion by an order of magnitude and therefore changes it entirely.
Confirming post #114 from a second method, which matters more than confirming it from a second person.
Reading the barrel at eye level matters more than any equipment choice. Parallax at a shallow angle is enough to shift a reading by a graduation.
The variance between people here is larger than the effect being discussed.
Where I have landed on 0.3 ml versus 0.5 ml, having got it wrong once in public: the direction is clear, the magnitude is not, and anyone quoting a precise magnitude has borrowed it from somewhere that did not measure it.
Reading rather than contributing, but this is the most useful thread I have found on it.