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c/reconstitution·posted 4 months ago by u/swirl_dont_shake

[Discussion] can we stop arguing about dead space until somebody posts a number

Discussion Long Haul ×8 Slow Clap ×1 Clean Column ×1

insulin syringe. That is the whole post, but I will justify it.

Everything else people worry about in c/intlshipping is downstream of it. Titration speed, reflux, the endless dose arguments — most of it resolves if you sort insulin syringe out first, and almost nobody does.

I say this having got it wrong for 12 months. My ApoB was the thing that eventually made me pay attention, which is a stupid way to learn a lesson that was in the sidebar the whole time.

2,847 up / 195 down94% upvoted49 commentsid 41rry45 Mar 2026

49 comments

28 in this archive, depth 4

best — the order this archive was captured in

u/marta_weiss315 points·4 months ago·edited

the concentration on the vial in marker is the most important step

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u/hedda_ekstrom177 points·4 months ago·edited

the concentration on the vial in marker is the most important step

Disagree on that part. 97.4% and 97.4% on the same vial is normal.

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u/escrow_evangelist223 points·4 months ago

10mg vial, 2mL water, concentration is 10/2 — write it on the vial afterwards

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u/reflux_report108 points·4 months ago

the concentration on the vial in marker is the most important step

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u/freya_onwuka90 points·4 months ago

dosing errors come from people reconstituting two vials differently and forgetting which is which

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u/aurel_boateng151 points·4 months ago·edited

Not convinced. The evidence does not support that reading.

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u/vito_beaulieu178 points·4 months ago

Disagree but this is the good kind of wrong — it is specific enough to be checked.

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u/oskar_kaufmann43 points·4 months ago

5mg vial, 2mL water, concentration is 5/2 — write it on the vial afterwards

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u/tomas_kimani21 points·4 months ago

Not convinced. The evidence does not support that reading.

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u/swirl_dont_shakeOPreconstitution122 points·4 months ago

Dead space ate 12 units on a low-volume draw. Tiny impact at 1.0mg, massive impact at 1.7mg.

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u/spain_receta65 points·4 months ago

u-100 syringe, not u-40, or your math is off by factor of 10

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u/rina_bergstrom21 points·4 months ago

u-100 syringe, not u-40, or your math is off by factor of 10

Yes, exactly this, and it is the bit that took me 90 weeks to accept.

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u/emeka_delgado166 points·4 months ago

dead space is real and the syringe matters

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u/anjali_tamm58 points·4 months ago

show your working or it is unhelpful

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u/bruno_dumitru134 points·4 months ago·edited

Yeah, showing the arithmetic is the fastest way for someone to spot the error.

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u/swirl_dont_shakeOPreconstitution69 points·4 months ago

Dead space ate 15 units on a low-volume draw. Tiny impact at 0.5mg, massive impact at 12.5mg.

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u/marisol_frisk101 points·4 months ago

the concentration on the vial in marker is the most important step

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[deleted]40 points·4 months ago

[deleted]

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u/aurel_boateng78 points·4 months ago

dosing errors come from people reconstituting two vials differently and forgetting which is which

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u/cardio_endpoint_c-28 points·4 months ago

Dead space in the needle hub holds a small but non-trivial volume. On low-volume draws that can be several units.

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u/swirl_dont_shakeOPreconstitution1 point·4 months ago

Spent 19 weeks confused about concentration math until someone showed me the table. 5mg, 2mL, concentration is 5/2.

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u/arne_restrepo45 points·4 months ago·edited

Disagree. What you are describing is consistent with bacteriostatic water, not with what you concluded.

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u/swirl_dont_shakeMOD16 points·4 months ago

Retitled to remove editorialising. Put the evidence in the body.

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u/adaeze_cabrera4 points·4 months ago

Retitled to remove editorialising.

Counter-anecdote: opposite result, same dose. Which mostly tells us the variance is huge.

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u/tomas_kimani13 points·4 months ago·edited

dosing errors come from people reconstituting two vials differently and forgetting which is which

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u/india_generic_g36 points·4 months ago

Crossposting this to c/sideeffects because the people who need it are not reading this community.

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u/bac_water_banditreconstitution11 points·4 months ago·edited

What was the vial size and how much bac water?

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u/nadia_kjaer25 points·4 months ago

u-100 syringe, not u-40, or your math is off by factor of 4

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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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