This gets cited here weekly, usually second-hand, so it is worth setting out what it does and does not establish.
Concentration choice is a precision decision, not a preference. Reconstitute high and every dose is a tiny volume where one unit of syringe error is a large fraction of the dose. Reconstitute low and you get more graduations per dose, so the same hand tremor costs proportionally less. Against that, more diluent means more benzyl alcohol and a shorter comfortable in-use window.
Where I think it is weakest: the subgroup findings are the part I trust least — with enough subgroups something is always significant, and these were not all pre-registered.
The question I want answered is how much material I am losing to dead space, and whether that explains why a 10mg vial gives me nine usable draws rather than ten. Tell me what I have not thought of.
Figures above are from the primary publication rather than the press summary. If a number here disagrees with one you have, post yours and we will work out which of us is reading a secondary source.
SarahChen_PharmD said:Concentration choice is a precision decision, not a preference.
Agreeing with SarahChen_PharmD, and the qualification matters more than the agreement. Dead space is the answer to the missing dose. A fixed-needle insulin syringe holds a few microlitres in the hub and needle after the plunger bottoms out, and on small draws that is a measurable percentage of every dose. Across ten draws it adds up to most of an eleventh, which is exactly the "nine draws from a ten-dose vial" complaint. Luer-lock syringes are worse; low-dead-space fixed-needle designs are better.
SarahChen_PharmD said:Concentration choice is a precision decision, not a preference.
I am going to disagree with reconstituting low as a general rule. More diluent, more punctures, more in-use days at room temperature, and the stability trade-off is real. Precision is not the only variable being optimised.
That is the short version; the long version is somebody else's post.
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Browse GL BiochemShort answer first, then the reasoning. Do it in two steps and it stops being confusing. First concentration: 10mg into 2ml is 5mg/ml. Then volume: a 0.5mg dose is 0.5 ÷ 5 = 0.1ml. Then units, and this is where people go wrong — a U-100 syringe is graduated in hundredths of a millilitre, so 0.1ml is 10 units. The word "units" has nothing to do with milligrams; it is a volume marking that exists because insulin happens to come at 100 units per ml.
Dr.RaviCardio said:Dead space is the answer to the missing dose.
Same experience, arrived at from the opposite direction.