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If I reconstitute a 20 mg vial with 1.5 mL of bacteriostatic water, what concentration do I end up with?

Asked 28 Dec 2025Modified 7 months agoViewed 4.6k times
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What I am working with: 20 mg · 1.5 mL · bacteriostatic water.

I have worked this out and I would like someone to find the error, because I suspect there is one.

My working so far, for the record, is below, and I am fairly sure the error is in the unit conversion rather than the algebra.

Is my approach right even if my number is wrong?

reconstitution
reconstitution

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The arithmetic itself: milligrams to millilitres to insulin units, concentration after reconstitution, dose per draw, and vial-days per vial. Show…

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Water for injection containing roughly 0.9 per cent benzyl alcohol as a bacteriostatic agent. It suppresses growth in a multiple-withdrawal vial;…

149 questions
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askedpriya_menon13k3528 Dec 2025
Add whether the needle is fixed or detachable — the dead space differs by an order of magnitude. – plate_count_9k 4 months ago
How many draws are you planning from the vial? That decides which diluent to use. – Dr_Otto_Lindqvist 3 months ago
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