u/katrin_marchetti

I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.

Who does this help, and who does it cost?

Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.

soren_zamora has the units point exactly right. They are a volume on the barrel and nothing else.

more water is not more drug, it is the same drug in a bigger volume

Careful — you have a plausible mechanism and no evidence that it is the operative one in the case you are describing.

units are a volume on a U-100 syringe, not a dose

Spent 3 weeks confused about this until somebody drew the table for me. 20mg, 2mL, 10mg/mL, 1.5mg is 15 units. That is the whole thing.

reconstituting at a round concentration makes every later dose easy

Yes — a proposal with concrete wording gets discussed. A complaint about the rules in general does not.

Yes. Nobody here is paid and the disclosure page says so in tedious detail, which is the correct level of tedious.

What breaks if we make that change?

What concentration did you actually reconstitute at, rather than what did you intend to?

Bacteriostatic water contains benzyl alcohol as a preservative, which is what makes repeated entry into the same vial reasonable. Plain sterile water has no preservative.

Have you read the published formula, genuinely asking?

Not quite. Bacteriostatic and sterile water are not interchangeable for a multi-draw vial, and the difference is the preservative.

aim the stream at the glass wall, not at the cake

Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.

A rule-change proposal needs replacement wording because that is what can be evaluated. Without it there is nothing to compare against the current text.

read the discussion section, that is where the honesty lives

Small fix — a U-100 syringe is 100 units per mL. If yours is marked differently it is not U-100 and the whole calculation changes.

more water is not more drug, it is the same drug in a bigger volume

The lyophilised cake displaces a small volume, so the true concentration is very slightly lower than the arithmetic suggests. It is a fraction of a percent and it is dwarfed by fill tolerance.

Correction: that is glucose-dependent insulin secretion, which is why hypoglycaemia risk is low as monotherapy. Not the same claim as you made.

The arithmetic in full: concentration is mass over volume, so 30mg into 2mL gives 15mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 1.5mg is 1.5 divided by 15 millilitres, which is 10 units.

aim the stream at the glass wall, not at the cake

Are you accounting for the powder volume, or is that where the confusion is?

If your calculation produces a fraction of a unit, the concentration is wrong for your dose. Change the water volume until the numbers land on whole units.

Tried to build a mental model from mechanism alone and produced a confident prediction that the trial data flatly contradicted.

bacteriostatic water has the preservative, sterile water does not

glucagon agonism sounds paradoxical until you read the energy expenditure work

Not convinced by the proposal as worded. It would remove the specific thing that makes the vendor board usable.

Show the arithmetic — where did the unit figure come from?

nobody here is paid, including the moderators

receptor agonism is not the same as receptor activation in every tissue

Wrote the date on the vial as well as the concentration after losing track of which one was opened first.

Right, and the arithmetic behind it: 5mg in 2mL is 2.5mg/mL, so 1mg is 40 units.

That only works if the fill weight is exactly the label weight, and it usually is not exactly anything.