three years of dead space threads, summarised so you do not have to read them
three years of dead space threads, summarised so you do not have to read them. Not a hot take, just something I have not seen said plainly here.
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.
Why "more water" keeps confusing people, including me for a month.
The vial contains a fixed amount of peptide. Water changes nothing about that amount. What it changes is concentration, and concentration is the divisor between the dose you want and the volume you draw.
So doubling the water halves the concentration and doubles the units for the same dose. Nothing is diluted in any sense that matters; you are simply reading a bigger number off the same barrel. Pick the water volume that puts your usual dose on a whole number of units and life gets easier.
The failure modes I have actually seen posted here, in order of frequency.
One: reconstituting at a different volume than intended and not writing it down, so the next draw is based on a remembered concentration. Two: treating units as a dose rather than a volume, which breaks the moment the concentration changes. Three: assuming a syringe is U-100 when it is not.
All three are solved by the same two habits — do the arithmetic before the water goes in, and write the result on the glass. Neither costs anything and between them they cover almost every question this board gets.
Tell me where this is wrong. That is the useful part of posting it.
best — the order this archive was captured in
Aim the stream down the wall of the vial rather than into the cake. Reconstitution is a solubility problem, not a mixing problem, and mechanical shear does nothing helpful.
twice as much water halves the concentration and doubles the units for the same dose
10mg into 2mL is 5mg/mL, and 2.5mg of that is 50 units
bacteriostatic water has the preservative, sterile water does not
Careful — that arithmetic is wrong. 10mg in 2mL is 5mg/mL, so 1mg draws to 20 units, not what you wrote.
Show the arithmetic — where did the unit figure come from?
Same. I got this wrong once, caught it because the units looked absurd, and have written on every vial since.
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
a U-100 syringe reads 100 units to the millilitre, every time
The arithmetic in full: concentration is mass over volume, so 10mg into 2mL gives 5mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 2mg is 2 divided by 5 millilitres, which is 40 units.
Correction: that gives 10 units, not what you have written. 30mg into 2mL is 15mg/mL and the division follows from there.
Correction: that gives 10 units, not what you have written.
Adding one thing — put the date on the label too. Concentration plus date and you can never mix two vials up.
the number you write down is the number you will trust at 6am
What concentration did you actually reconstitute at, rather than what did you intend to?
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.
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.
units are a volume on a U-100 syringe, not a dose
Bacteriostatic water contains benzyl alcohol as a preservative, which is what makes repeated entry into the same vial reasonable.
This is the sentence that makes the rest unnecessary. Write it on the vial and the problem is gone.
reconstituting at a round concentration makes every later dose easy
more water is not more drug, it is the same drug in a bigger volume
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
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.
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