does dead space actually matter or is it forum lore at this point
does dead space actually matter or is it forum lore at this point. If this has been answered properly somewhere, link me and I will delete.
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.
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.
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.
Tell me where this is wrong. That is the useful part of posting it.
best — the order this archive was captured in
Reminder: this board does maths, not dosing. Nobody here tells another member what amount to take.
swirl, never shake
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Yes, and the dead-space point is worth repeating: it is small, it is real, and it is the same for every draw.
Research-use-only material is not approved for human use, so treat everything in this thread as arithmetic about solutions rather than instructions for a person.
Adding more water does not change how much peptide is in the vial. It changes the concentration, which changes the volume you draw for the same amount. That is the entire relationship.
Correcting myself above: I wrote the concentration the wrong way up. Mass over volume, not volume over mass.
Spent 18 weeks confused about this until somebody drew the table for me. 20mg, 2mL, 10mg/mL, 5mg is 50 units. That is the whole thing.
Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.
Pushback on the syringe advice: a U-100 barrel reads units of volume. Calling them "doses" is how the confusion starts.
Yes. Writing 5mg/mL on the vial takes four seconds and removes the entire class of error this board exists to fix.
Correction: that gives 10 units, not what you have written. 30mg into 3mL is 10mg/mL and the division follows from there.
label the vial with the date as well as the concentration
the powder cake sits at the bottom, the volume you add is the volume that counts
The dead space question sent me down a rabbit hole for a week. It is a fraction of a unit and it is the same every draw.
do the arithmetic before you reconstitute, not while holding a syringe
How many mg in the vial and how many mL are you adding?
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.
Cosigning the round-number approach. Reconstituting to something awkward is how you end up drawing 27.5 units at six in the morning.
This. Showing the working is the fastest way for somebody else to spot the mistake.
units are a volume on a U-100 syringe, not a dose
bacteriostatic water has the preservative, sterile water does not
5mg into 2mL is 2.5mg/mL, and 1.5mg of that is 60 units
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
Agreed on the swirl. There is no reason to shake it and a good reason not to.
Agreed — units are volume. Once that lands, the rest of the arithmetic is one division.
Same. I got this wrong once, caught it because the units looked absurd, and have written on every vial since.
reconstituting at a round concentration makes every later dose easy
if the maths gives you a fraction of a unit, change the concentration
Reconstituted at 1mL when I meant to use a different volume. Caught it because the units looked wrong on the barrel. Now I write 20mg/mL on the glass before I put the cap back.
- 1How many mg in the vial and how many mL are you adding?12 comments in this branch · started by u/spain_receta