c/reconstitution wiki

What this community is for

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.

c/reconstitution was created on 27 Aug 2023 and currently has 88,100 members and 130 captured submissions. It sits in the busiest tier of the site, which mostly affects how fast a question gets answered rather than how well.

Rules, and why each exists

Community rules come first, then the six site-wide rules that apply everywhere on GLP Research Hub. Community rules are enforced by the moderators listed at the bottom of this page; site rules are enforced by everyone.

1. Show your numbers. "How many units?" with no mg and no mL cannot be answered.
2. Never post a calculation as advice without stating the concentration it assumes.
3. No sterile-compounding-for-others discussion. Personal handling only.

And the site rules, which are short on purpose:

1. Independent community. Nobody here sells anything, and anyone who tries is banned.
2. Not medical advice. Describe what you did; never prescribe to a stranger.
3. Claims need evidence. Batch numbers, dated screenshots, independent test reports, or a citation.
4. No referral links, discount codes or affiliate URLs. Permanent ban, no appeal.
5. No contact handles, wallet addresses or tracking numbers — they identify people.
6. Be recognisably decent. Disagree hard, insult nobody.

Terms you will see

Vocabulary that turns up constantly in c/reconstitution. Each links to the topic page, which collects every submission that touches it.

• reconstitution — adding liquid to a lyophilised vial; a concentration choice, not a dose choice.
• bacteriostatic water — water with 0.9% benzyl alcohol; the preservative is why an in-use window exists.
• mg/mL — concentration — milligrams in the vial divided by millilitres added.
• units — syringe volume markings. On a U-100 syringe one unit is 0.01 mL. Not milligrams.
• insulin syringe — U-100 graduated syringe; the 0.3mL size is the one that prevents overdoses.
• dead space — liquid held in the needle hub that never gets injected; a consistent offset.
• concentration — mass of drug per unit volume after reconstitution.

Start here

The twelve highest-scoring submissions in this community. Not necessarily the most correct — the most agreed-with, which is a different thing, and worth remembering when you read them.

1. [PSA] mg/mL is not what most of this community thinks it is — 12k points, 23 comments, 2 years ago
2. bacteriostatic water is the most under-discussed thing on this board — 11k points, 32 comments, 1 year ago
3. units are the most under-discussed thing on this board — 9.2k points, 36 comments, 1 year ago
4. [Meta] proposal — a flair for units posts — 8.8k points, 59 comments, 2 years ago
5. unpopular opinion: most of what gets said here about reconstitution is guesswork — 8.4k points, 46 comments, 2 years ago
6. three years of units threads, summarised so you do not have to read them — 7.8k points, 38 comments, 1 year ago
7. how much of what we believe about reconstitution actually comes from concentration threads — 7.3k points, 47 comments, 2 years ago
8. the units thing finally clicked for me and I want to write it down — 7.2k points, 41 comments, 6 months ago
9. how much of what we believe about concentration actually comes from reconstitution threads — 6.4k points, 28 comments, 1 year ago
10. genuine question about bacteriostatic water that I am slightly embarrassed to ask — 6.4k points, 42 comments, 1 year ago
11. [Discussion] we are measuring units at the wrong time and calling it noise — 6k points, 22 comments, 1 year ago
12. the reconstitution thing finally clicked for me and I want to write it down — 5.4k points, 14 comments, 1 year ago

Asked constantly

• [Question] does needle dead space actually matter at 2.5mg doses
• cored the stopper on day 9. rotate your puncture site
• cloudy after reconstitution — discard, right? right.
• [Question] how do you actually verify concentration
• how much of what we believe about mg/mL actually comes from reconstitution threads
• [Question] how do you actually verify dead space
• unpopular opinion: most of what gets said here about bacteriostatic water is guesswork
• [Question] dead space — what am I missing here
• how much of what we believe about concentration actually comes from mg/mL threads
• [Meta] the mg/mL rule is doing its job and people should stop complaining

If your question is on that list, read the answers there first. If it is not, ask it — that is what the community is for, and "this has been asked" is only a helpful reply when it comes with a link.

Who runs this

Moderation here is done by volunteers who also post as normal members. They are not clinicians, not vendors, and not paid.

• u/bac_water_bandit — Bacteriostatic water, 0.9% benzyl alcohol, 28 days, room temp after first puncture. Write it down.
• u/vial_math_vera — mg in vial ÷ mL added = mg/mL. Everything else is arithmetic you can check.
• u/units_not_mg — Every dosing mistake I have seen came from confusing units with milligrams.
• u/swirl_dont_shake — You are not making a cocktail. Roll it between your palms.