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c/reconstitution·posted 7 months ago by u/hedda_ekstrom

[Meta] the dead space rule is doing its job and people should stop complaining

Math Clean Column ×6 Slow Clap ×2

Genuinely asking, not being difficult.

Everyone in c/cagrilintide repeats that dead space is important. I believe it, but I have never seen anyone show why, and when I search I get 7 threads of people agreeing with each other.

Is there a paper? Is there a measurement? Or is this one of those things that is true because it has been repeated since 2023?

I am not trying to be the "source?" guy. I would just like a source.

12,501 up / 10,910 down53% upvoted33 commentsid 87inuq5 Dec 2025

33 comments

30 in this archive, depth 5

best — the order this archive was captured in

u/vito_beaulieu364 points·7 months ago

Half-life is about 168 hours, so steady state lands around week 24–5. Practical consequence: what you feel in week 1 is not what that dose does.

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u/dilara_szabo98 points·7 months ago·edited

The confident tone is doing a lot of work that the evidence is not.

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u/hedda_ekstromOP235 points·7 months ago

Small correction: the trial was 18 weeks, not 7. Does not change your point but people will quote it.

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u/ismael_nwosu59 points·7 months ago

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

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u/hedda_ekstromOP31 points·7 months ago

20mg vial, 1mL water, concentration is 20/1 — write it on the vial afterwards

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[removed]15 points·7 months ago

[removed by moderator]

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u/hedda_ekstrom116 points·7 months ago

swirl, do not shake, or you are courting oxidation

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u/signe_grimaldi148 points·7 months ago

Half-life is about 168 hours, so steady state lands around week 24–5.

Yes, exactly this, and it is the bit that took me 57 weeks to accept.

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u/swirl_dont_shakeMOD192 points·7 months ago

Flair changed to match the content. Read the sidebar before posting next time and we are square.

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u/escrow_evangelist227 points·7 months ago

never post a calculation as advice without stating the concentration

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u/mateusz_achebe163 points·7 months ago

dead space is real and the syringe matters

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u/lyophile_lou44 points·7 months ago

Show the arithmetic. Where did the units come from?

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u/kavya_radich22 points·7 months ago·edited

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

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u/liv_nkemelu95 points·7 months ago

Spent 22 weeks confused about concentration math until someone showed me the table. 15mg, 2mL, concentration is 15/2.

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u/priya_guerrero76 points·7 months ago

20mg vial, 2mL water, concentration is 20/2 — write it on the vial afterwards

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u/nadia_kjaer85 points·7 months ago·edited

more water means more units for the same dose, which means finer resolution

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u/hedda_ekstromOP31 points·7 months ago

Respectfully this is a sample of one presented as a finding.

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u/britta_nakamura83 points·7 months ago

Two vials, two different concentrations, forgot which was which, almost made a 9 times error. Now I label everything.

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u/honest_syringe_maybe22 points·7 months ago

stopper coring on the 20th draw because you keep using the same entry point. rotate.

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u/alcohol_aversion-22 points·7 months ago

bacteriostatic and sterile water are not interchangeable, do not use them that way

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u/ruben_cabrera9 points·7 months ago

stopper coring on the 20th draw because you keep using the same entry point.

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

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u/cesar_ivaturi54 points·7 months ago

Reconstituted at 2mL when I meant 13mL. Caught it because the units looked wrong. Write the concentration.

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u/rasmus_kuipers37 points·7 months ago

stopper coring on the 20th draw because you keep using the same entry point. rotate.

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u/quarter_dose_queenlow and slow27 points·7 months ago

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

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u/priya_guerrero18 points·7 months ago

Slight fix: the number was 99.3, not 93.7. Decimal point, but a fairly consequential one.

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u/piotr_bruun35 points·7 months ago

Two vials, two different concentrations, forgot which was which, almost made a 9 times error.

Adding to this: insulin syringe is doing more work than the comment implies.

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u/elodie_grimaldi57 points·7 months ago

swirl, do not shake, or you are courting oxidation

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u/aurel_boateng38 points·7 months ago

never post a calculation as advice without stating the concentration

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u/tomas_kimani32 points·7 months ago

never post a calculation as advice without stating the concentration

Yes, exactly this, and it is the bit that took me 81 weeks to accept.

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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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