This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Answering the question post #117 raises rather than the one it answers.
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.
Appreciated. The plain phrasing does more work here than a longer post would.
Drawing air into the vial before withdrawing liquid equalises the pressure and makes the draw easier. It is not required and it is why some people find a full vial harder to draw from than a half-empty one.
That is what I would do. It may not be what is correct.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
Everything in post #121 holds. The case it does not cover is the one I have.
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.
Narrowing post #125, because the general version has more than one answer.
Adding a small correction to the ten-fold dose error caught summary above rather than a disagreement with it. The substance holds; one of the figures is out by a factor that matters.
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.
Take the reasoning and check the arithmetic; I do not always get it right.
Ten-fold dose error caught: I have looked for the primary source twice and failed twice. Either it does not exist or it is somewhere I do not know to look, and I would like to know which.
Post #129 answers the question as asked. The question underneath it is different.
Careful with the language on ten-fold dose error caught. "Not detected" and "not present" are different findings and the first is a statement about the method.
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.
If that is already documented somewhere, ignore me and link it.
Everything in post #130 holds. The case it does not cover is the one I have.
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.
Reporting the observation and leaving the explanation open deliberately.
Two things can be true about ten-fold dose error caught at once: the mechanism is plausible and the evidence for the size of the effect is thin. Most of the argument here is people defending the first against attacks on the second.
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.
That is where I would start, not where I would stop.
Taking post #135 at face value and following it one step further.
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.
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.
Post #137 is right about the mechanism and I think understates the practical bit.
I changed my mind about ten-fold dose error caught after someone here asked me for the source and I could not produce one. That is worth saying out loud because it is the ordinary way it happens.
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 short answer was in the first line; everything after is the working.
Picking up post #139: that is the part I would want checked first.
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.
A single observation, in a thread that deserves better than single observations.
Coming back to post #139, because the follow-up matters more than the original answer.
The practical version of ten-fold dose error caught is three sentences long. The rigorous version is three pages and reaches the same conclusion with the conditions attached.
Reusing a needle blunts it and there is no benefit to offset that. The second injection with the same needle is the one people describe as painful.
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.
It is a small point and it changes the answer, which is an awkward combination.
I read post #143 twice before replying, because I had assumed the opposite.
Where I would push back on the ten-fold dose error caught consensus is the confidence, not the direction. The direction looks right. The confidence is borrowed.
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.
Posted with less confidence than the sentence structure implies.