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[Question] how do you actually verify concentration

Question Well Actually ×5 Slow Clap ×3 Cold Box ×1

Been lurking in c/semaglutide for about 21 months and finally have something worth posting.

Short version: week 51, 5mg, and mg/mL is the bit I still cannot get a straight answer on. I have read the wiki, I have read the last 35 threads, and the answers split roughly down the middle.

What I actually want to know is whether the people saying it does not matter have measured it, or whether it is just repeated confidently. Happy to be told I am overthinking this — I probably am — but I would rather overthink it now than at week 45.

7,449 up / 790 down90% upvoted43 commentsid kv9qbv9 Jul 2024

43 comments

29 in this archive, depth 5

best — the order this archive was captured in

u/hub_opssite staff817 points·2 years ago

Titration speed is a side-effect dial far more than an efficacy dial.

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u/vial_math_verasyringe math458 points·2 years ago

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

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u/emil_okwuosa200 points·2 years ago

This is correct. 2mL versus 4mL is the common mistake.

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u/alcohol_aversion291 points·2 years ago

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

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u/janek_ferrari241 points·2 years ago

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

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u/RetaAndRegret20 points·2 years ago

stopper coring on the 4th draw because you keep using the same entry point. rotate.

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u/ahmed_rasmussen1 point·2 years ago

Is that 15mg vial or 5mg?

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[deleted]1 point·2 years ago

[deleted]

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u/quarter_dose_queenlow and slow1 point·2 years ago·edited

Show the arithmetic. Where did the units come from?

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u/quarter_dose_queenOPlow and slow1 point·2 years ago

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

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u/sofia_danquah389 points·2 years ago

show your working or it is unhelpful

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u/swirl_dont_shakereconstitution307 points·2 years ago·edited

This is the "correlation is mechanism" thing again. You changed three variables at once.

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u/marta_weiss-6 points·2 years ago

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

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u/ruben_cabrera185 points·2 years ago

Is that 15mg vial or 31mg?

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u/rosa_mensah89 points·2 years ago

i am begging people to write down the concentration

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u/tuva_kirchner42 points·2 years ago

Cosigning. The concentration on the vial in marker is load-bearing.

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u/alcohol_aversion153 points·2 years 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/aurel_boateng92 points·2 years ago

The single most useful thing I did was write the concentration on the vial. Stopped all the confusion after that.

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u/aleksi_lehtinen32 points·2 years ago

i am begging people to write down the concentration

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u/dilara_szabo20 points·2 years ago

Not convinced. The evidence does not support that reading.

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u/arne_restrepo117 points·2 years ago

This is correct. 2mL versus 2mL is the common mistake.

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u/elodie_grimaldi138 points·2 years ago

This is the "correlation is mechanism" thing again. You changed three variables at once.

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u/quiet_reader_9942 points·2 years ago

dead space is real and the syringe matters

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u/britta_nakamura53 points·2 years ago

Show the arithmetic. Where did the units come from?

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u/sleep_apnea_sam35 points·2 years ago

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

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u/signe_grimaldi22 points·2 years ago

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

Disagree on that part. 99.3% and 93.7% on the same vial is normal.

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u/reflux_report10 points·2 years ago

swirl, do not shake, or you are courting oxidation

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u/india_generic_g81 points·2 years ago

Dead space in the needle hub holds a small but non-trivial volume.

Yes, exactly this, and it is the bit that took me 65 weeks to accept.

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u/janek_ferrari22 points·2 years ago

15mg vial, 1mL water, concentration is 15/1 — write it on the vial afterwards

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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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