someone explain insulin syringe to me like I have not read a paper in years
The title is the whole question — someone explain insulin syringe to me like I have not read a paper in years — but here is why I am asking.
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.
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.
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.
Would rather be corrected in public than confident in private.
best — the order this archive was captured in
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.
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.
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bacteriostatic water has the preservative, sterile water does not
Agreed — units are volume. Once that lands, the rest of the arithmetic is one division.
Wrote the date on the vial as well as the concentration after losing track of which one was opened first.
Pushback on the syringe advice: a U-100 barrel reads units of volume. Calling them "doses" is how the confusion starts.
The arithmetic in full: concentration is mass over volume, so 15mg into 3mL gives 5mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 1.5mg is 1.5 divided by 5 millilitres, which is 30 units.
the number you write down is the number you will trust at 6am
Disagree with the "more water is safer" framing. It is not safer, it is just a different number to divide by.
Same. I got this wrong once, caught it because the units looked absurd, and have written on every vial since.
the number you write down is the number you will trust at 6am
Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.
Asked WXT what volume they reconstitute to for their own stability testing and they answered in one line. Useful thing to know.
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.
Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.
Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.
Correction: that gives 10 units, not what you have written. 10mg into 1mL is 10mg/mL and the division follows from there.
Agreed on the swirl. There is no reason to shake it and a good reason not to.
Did the maths give you a whole number of units, or a fraction?
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
Not quite. Bacteriostatic and sterile water are not interchangeable for a multi-draw vial, and the difference is the preservative.
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.
Spent 18 weeks confused about this until somebody drew the table for me. 10mg, 2mL, 5mg/mL, 2mg is 40 units. That is the whole thing.
the powder cake sits at the bottom, the volume you add is the volume that counts
units are a volume on a U-100 syringe, not a dose
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
Careful — that arithmetic is wrong. 30mg in 3mL is 10mg/mL, so 2.5mg draws to 25 units, not what you wrote.
Reconstituted at 3mL when I meant to use a different volume. Caught it because the units looked wrong on the barrel. Now I write 10mg/mL on the glass before I put the cap back.
Corrected the concentration in the title, which contradicted the body. Nothing else touched.
- 1Started reconstituting everything to a round concentration and the…14 comments in this branch · started by u/runa_grimaldi
- 2The arithmetic in full: concentration is mass over volume, so 15mg into 3mL…7 comments in this branch · started by u/ilias_cabrera