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c/reconstitution·posted 1 months ago by u/elin_ferrari

[Discussion] insulin syringe is doing more work than we give it credit for

Discussion Receipts ×3 Slow Clap ×1

The title is the argument: insulin syringe is doing more work than we give it credit for. Here is the rest of it.

Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.

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.

Shook the first vial because nobody told me not to. It was fine, but I have swirled every one since.

Not medical advice, obviously, and nothing here is approved for human use. One person with a spreadsheet.

9,724 up / 7,126 down58% upvoted37 commentsid 14ei0t5 Jun 2026

37 comments

11 in this archive, depth 6

best — the order this archive was captured in

u/ismael_nwosu514 points·1 months ago

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.

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u/cesar_ivaturi-28 points·1 months ago

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.

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u/hedda_ekstrom218 points·1 months ago

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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u/mateusz_achebe132 points·1 months ago·edited

Spent 13 weeks confused about this until somebody drew the table for me. 20mg, 2mL, 10mg/mL, 5mg is 50 units. That is the whole thing.

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u/emil_zamora34 points·1 months ago

the number you write down is the number you will trust at 6am

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u/honest_syringe_maybe24 points·1 months ago

Asked GGPeps what volume they reconstitute to for their own stability testing and they answered in one line. Useful thing to know.

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u/alcohol_aversion7 points·1 months ago

dead space in the needle hub is real and it is small

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u/rasmus_mensah5 points·1 months ago

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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About c/reconstitution

The arithmetic and the technique. Bacteriostatic versus sterile water, reconstitution volume as a concentration choice, converting mg/mL into insulin-syringe units, dead space, swirl-not-shake, stopper coring, and how long a reconstituted vial is actually good for. Math errors get corrected fast and politely.

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