[2026 update] 0.3 mL versus 0.5 mL versus 1 mL barrels: resolution matters posts 61–90
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.
Dead volume: residual liquid in the hub and needle after withdrawal. Typical residual is 0.01 to 0.02 mL for an insulin syringe with a fixed needle. Accounting for it matters if precision matters.
Answering the question post #63 raises rather than the one it answers.
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.
The disagreement above is smaller than it looks once the terms are fixed.
Confirming post #64 from a second method, which matters more than confirming it from a second person.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
Where I would look next, rather than where I would stop.
I had written a reply contradicting post #63 and deleted it. Here is what survived.
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.
That much is documented. The rest is how I have interpreted it.
For anyone finding this later: the short answer on 0.3 ml versus 0.5 ml is that it depends on one thing, and the rest of the thread is people identifying which thing.
Collapsed as off-topic by two members at trust level 3 or above
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.
Post #66 and I disagree about the size of the effect, not about the direction.
Worth separating 0.3 ml versus 0.5 ml as a question about the compound from 0.3 ml versus 0.5 ml as a question about the documentation. They get answered by different people and only one of them is answerable here.
Confirming post #70 from a second method, which matters more than confirming it from a second person.
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.
A qualification I should have led with rather than closed on.
Two questions I would want answered before drawing anything from the 0.3 ml versus 0.5 ml data above: how were the cases selected, and what happened to the ones that dropped out.
Adding a small correction to the 0.3 ml versus 0.5 ml summary above rather than a disagreement with it. The substance holds; one of the figures is out by a factor that matters.
Post #73 describes the usual case. This is about the unusual one.
The thing about 0.3 ml versus 0.5 ml that took me longest to accept is that a plausible mechanism is not evidence of an effect. It is a reason to look, not a result.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
I have no interest in any supplier named above.
Post #77 put the caveat in the right place and I want to underline it.
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.
That matches what I was told, which is not the same as knowing it.
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.
A weak preference rather than a position.
Picking up post #78: that is the part I would want checked first.
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.
Filing this under things that are true until someone shows me otherwise.
On post #80 — agreed on the reasoning, with one qualification.
My understanding of 0.3 ml versus 0.5 ml is a few years old and may have been superseded. If it has been, I would genuinely like to know rather than keep repeating it.
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 I have skin in this question and have tried to discount for it.
Dead volume: residual liquid in the hub and needle after withdrawal. Typical residual is 0.01 to 0.02 mL for an insulin syringe with a fixed needle. Accounting for it matters if precision matters.
That holds for the case as described. Change the assumptions and it may not.
I would be cautious about generalising from the 0.3 ml versus 0.5 ml example above. It is a good example. It is one example.
Where the 0.3 ml versus 0.5 ml discussion usually stalls is that nobody wants to say "I do not know" and everyone is willing to say "it varies". Those are the same sentence with different clothes on.