insulin syringe is the most under-discussed thing on this board
insulin syringe is the most under-discussed thing on this board. Making the case below, and I expect to lose some of it in the comments.
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.
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.
The arithmetic in full: concentration is mass over volume, so 30mg into 2mL gives 15mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 0.75mg is 0.75 divided by 15 millilitres, which is 5 units.
That is everything I have. The rest is opinion and I have tried to keep it out.
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.
Agreed on the swirl. There is no reason to shake it and a good reason not to.
Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.
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bacteriostatic water has the preservative, sterile water does not
more water is not more drug, it is the same drug in a bigger volume
What is written on the vial right now?
What concentration did you actually reconstitute at, rather than what did you intend to?
Show the arithmetic — where did the unit figure come from?
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
Are you accounting for the powder volume, or is that where the confusion is?
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.
Pushback on the syringe advice: a U-100 barrel reads units of volume. Calling them "doses" is how the confusion starts.
How many mg in the vial and how many mL are you adding?
That only works if the fill weight is exactly the label weight, and it usually is not exactly anything.
Bacteriostatic or plain sterile water?
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
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.
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.
Spent 20 weeks confused about this until somebody drew the table for me. 20mg, 1mL, 20mg/mL, 2mg is 10 units. That is the whole thing.
if the maths gives you a fraction of a unit, change the concentration
label the vial with the date as well as the concentration
Correction: that gives 20 units, not what you have written. 5mg into 1mL is 5mg/mL and the division follows from there.
I would not round that figure. At 1.67mg/mL a rounding error of two units is a real fraction of the intended amount.
Disagree with the "more water is safer" framing. It is not safer, it is just a different number to divide by.
Not quite. Bacteriostatic and sterile water are not interchangeable for a multi-draw vial, and the difference is the preservative.
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.
Is that a U-100 syringe? The barrel markings change the answer completely.
dead space in the needle hub is real and it is small
- 1I keep a laminated card in the drawer with the arithmetic on it. Looks…14 comments in this branch · started by u/alcohol_aversion
- 2Agreed on the swirl. There is no reason to shake it and a good reason not to.9 comments in this branch · started by u/RetaAndRegret2