[PSA] let the alcohol swab dry before you puncture, that is the step everyone skips
let the alcohol swab dry before you puncture, that is the step everyone skips, and I say this having got it wrong myself for long enough to be annoyed about it.
The arithmetic in full: concentration is mass over volume, so 5mg into 1mL gives 5mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 0.75mg is 0.75 divided by 5 millilitres, which is 15 units.
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.
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.
Research-use-only material is not approved for human use and nothing here should be read as a recommendation to use it.
best — the order this archive was captured in
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.
Working has to be shown on arithmetic posts. Added a note asking for it rather than removing this one.
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.
10mg into 3mL is 3.33mg/mL, and 2.5mg of that is 75 units
Are you accounting for the powder volume, or is that where the confusion is?
units are a volume on a U-100 syringe, not a dose
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.
Shook the first vial because nobody told me not to. It was fine, but I have swirled every one since.
Asked KP what volume they reconstitute to for their own stability testing and they answered in one line. Useful thing to know.
I would not round that figure. At 20mg/mL a rounding error of two units is a real fraction of the intended amount.
Yes, and the dead-space point is worth repeating: it is small, it is real, and it is the same for every draw.
the number you write down is the number you will trust at 6am
Correction: that gives 10 units, not what you have written. 5mg into 2mL is 2.5mg/mL and the division follows from there.
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
write the concentration on the vial in marker, that is the whole post
That only works if the fill weight is exactly the label weight, and it usually is not exactly anything.
- 1Yes, and the dead-space point is worth repeating: it is small, it is real,…8 comments in this branch · started by u/saskia_mwangi
- 2Adding more water does not change how much peptide is in the vial. It…6 comments in this branch · started by u/sleep_apnea_sam