three years of units threads, summarised so you do not have to read them
three years of units threads, summarised so you do not have to read them, which sounds obvious until you try to state the evidence for it.
The arithmetic in full: concentration is mass over volume, so 20mg into 3mL gives 6.67mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 1mg is 1 divided by 6.67 millilitres, which is 15 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.
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.
I will update this if the picture changes rather than quietly leaving it up.
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.
Agreed on the swirl. There is no reason to shake it and a good reason not to.
dead space in the needle hub is real and it is small
the number you write down is the number you will trust at 6am
units are a volume on a U-100 syringe, not a dose
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
Careful — that arithmetic is wrong. 30mg in 3mL is 10mg/mL, so 5mg draws to 50 units, not what you wrote.
more water is not more drug, it is the same drug in a bigger volume
Reconstituted at 3mL when I meant to use a different volume. Caught it because the units looked wrong on the barrel. Now I write 1.67mg/mL on the glass before I put the cap back.
Agreed — units are volume. Once that lands, the rest of the arithmetic is one division.
twice as much water halves the concentration and doubles the units for the same dose
Wrote the date on the vial as well as the concentration after losing track of which one was opened first.
Wrote the date on the vial as well as the concentration after losing track of which one was opened first.
Adding one thing — put the date on the label too. Concentration plus date and you can never mix two vials up.
What concentration did you actually reconstitute at, rather than what did you intend to?
write the concentration on the vial in marker, that is the whole post
- 1Adding more water does not change how much peptide is in the vial. It…7 comments in this branch · started by u/ruben_cabrera