I reconstituted a 10mg vial with 2ml of bacteriostatic water and I want someone to check my unit arithmetic before I draw anything, because I keep getting two different answers.
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.
I would rather have one careful answer than five confident ones.
Answering the narrow version, because the broad one does not have a single answer. 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.
Ask again with the specifics and you will get a better answer than this one.
Dr.ReproEndo said:Concentration choice is a precision decision, not a preference.
Agreed, and it is worth saying that rounding to the nearest whole unit is usually acceptable at maintenance doses and is not acceptable at the bottom of a ladder, where one unit can be a fifth of the intended dose.
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Browse GL BiochemtampaLisa73 said:I reconstituted a 10mg vial with 2ml of bacteriostatic water and I want someone to check my unit arithmetic before I draw anything, because I keep…
Same position here, arrived at the long way round. 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.
That is the short version; the long version is somebody else's post.
From the other side of the consultation, briefly.
Just received my dosing arithmetic order — packaging review:
- Outer box: plain brown, no medication identifiers (discreet) ✅
- Inner insulation: Styrofoam with 3 gel ice packs ✅
- Temperature: vials were cold to touch on arrival ✅
- Labeling: lot number, BUD, compound name, concentration ✅
- Included: COA, reconstitution instructions, dosing card ✅
This is what professional compounding pharmacy shipping looks like. If your order arrives without these basics, reconsider your vendor.