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c/reconstitution·posted 9 months ago by u/quiet_reader_99

[Meta] proposal — a flair for reconstitution posts

Question Cold Box ×6

proposal — a flair for reconstitution posts — posting the reasoning in public because a policy you cannot inspect is just a preference.

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

Wrote the date on the vial as well as the concentration after losing track of which one was opened first.

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

Would rather be corrected in public than confident in private.

466 up / 10 down98% upvoted23 commentsid 19dw1p18 Oct 2025

23 comments

20 in this archive, depth 4

best — the order this archive was captured in

u/ahmed_rasmussen36 points·9 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/ines_ekstrom20 points·9 months ago

Disagree with the "more water is safer" framing. It is not safer, it is just a different number to divide by.

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u/quiet_reader_99OP28 points·9 months ago

Bacteriostatic water contains benzyl alcohol as a preservative, which is what makes repeated entry into the same vial reasonable.

Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.

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[deleted]11 points·9 months ago

[deleted]

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u/saskia_rahimi8 points·9 months ago

a U-100 syringe reads 100 units to the millilitre, every time

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u/honest_syringe_20257 points·9 months ago·edited

Same. I got this wrong once, caught it because the units looked absurd, and have written on every vial since.

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u/quiet_reader_99OP21 points·9 months ago

What is written on the vial right now?

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u/vito_beaulieu5 points·9 months ago·edited

Is that a U-100 syringe? The barrel markings change the answer completely.

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u/bac_water_banditreconstitution8 points·9 months ago

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.

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u/quiet_reader_99OP0 points·9 months ago

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.

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u/niels_roos0 points·9 months ago·edited

That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.

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u/ilias_steiner21 points·9 months ago

Not quite. Bacteriostatic and sterile water are not interchangeable for a multi-draw vial, and the difference is the preservative.

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u/oskar_ibarra10 points·9 months ago

How many mg in the vial and how many mL are you adding?

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u/rosa_mensah4 points·9 months ago·edited

How many mg in the vial and how many mL are you adding?

Adding one thing — put the date on the label too. Concentration plus date and you can never mix two vials up.

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u/saskia_mwangi16 points·9 months ago

I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.

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u/iman_falk10 points·9 months ago

Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.

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u/hedda_ekstrom3 points·9 months ago

Bacteriostatic or plain sterile water?

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u/ahmed_rasmussen1 point·9 months ago

Careful — that arithmetic is wrong. 15mg in 3mL is 5mg/mL, so 0.25mg draws to 5 units, not what you wrote.

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u/freya_onwuka1 point·9 months ago

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

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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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