This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Post #87 and I disagree about the size of the effect, not about the direction.
Check what the graduations actually say rather than what you expect. A syringe marked in units and one marked in millilitres look similar at a glance and are not the same instrument.
This is the sort of thing that ought to be settled and apparently is not.
Silicone coating on the barrel affects how smoothly the plunger moves and how a very slow injection feels. It is one reason two syringes at the same specification are not identical to use.
The disagreement above is smaller than it looks once the terms are fixed.
Marking my uncertainty on ten-fold dose error caught 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.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
Nothing to add on the substance. Thank you for taking the question at face value.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
Post #96 is right about the mechanism and I think understates the practical bit.
Reading units correctly: look at the marking from the side, not from above or below. The bottom of the plunger tip is the reading. Parallax error (wrong angle) is a source of dosing error.
Two claims get bundled together under ten-fold dose error caught 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.
Aspirating before injection: for subcutaneous injection, aspirating (pulling back on the plunger to check for blood) is not necessary and is sometimes discouraged because it is associated with more discomfort. Subcutaneous injection without aspiration is standard practice.
A qualification I should have led with rather than closed on.
Post #103 is right about the mechanism and I think understates the practical bit.
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.
The rule of thumb is fine; the edge cases are where it earns its keep.
A note on scope: what I am saying about ten-fold dose error caught applies to the case in the first post and I would not extend it further without checking.
Right — I had this wrong and I am glad to have read it before it mattered.
Confirming post #106 from a second method, which matters more than confirming it from a second person.
Drawing through a wider needle and injecting through a thinner one is a reasonable approach for a viscous preparation and pointless for an aqueous one.
I have deliberately not rounded that, because the rounding is where the argument starts.
Insulin syringe graduations: U-100 syringes are marked in units where 100 units = 1 mL. Always confirm your syringe is U-100. Confusion between insulin units and milligrams is the most common syringe error.
Caveat: everything above assumes the paperwork is what it says it is.
Taking post #108 at face value and following it one step further.
Needle length: typical lengths for subcutaneous injection are 4-6 mm (short), 8 mm (standard), or 10-12 mm (longer). Longer needles are needed for deeper tissue or if you have abdominal adiposity.
I would put the burden of proof on the interesting explanation, not the dull one.
I have been on both sides of the ten-fold dose error caught argument in this category within eighteen months, which should tell you how strong the evidence for either side is.
Noted, and thank you for writing it out rather than summarising it.
Building on post #110 rather than restating it.
Needle gauge: smaller numbers (30G) are finer and less painful. Larger numbers (25G) are courser. For subcutaneous injection, 27-30G is typical. Finer needles take longer to draw up but hurt less.
It cost nothing to check and would have cost something not to.
Needle length for subcutaneous delivery is a question about tissue depth and injection angle together. Short needles at ninety degrees and longer ones at an angle reach comparable depths.
Posting it because the silence on this was starting to look like agreement.
Posting my ten-fold dose error caught numbers with the method attached so they can be discounted properly. Uncontrolled, unblinded, and collected by someone who wanted a particular 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.
Where I part company with post #117, and it is a narrow parting.
Buying a box of the wrong barrel size is the most common regret described in this subcategory, and the reason is nearly always that the dose was decided after the syringes.
I would rather say I do not know than round it up to an answer.
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.
Happy to expand any of that if it is the useful part.