BenResearch_OR said:

Peptide reconstitution guide — BAC water volumes and concentrations Posting this as an important update for the other peptides & research compounds…

Agreeing with BenResearch_OR, and the qualification matters more than the agreement. The arithmetic is right and one caveat matters: a U-40 syringe changes the markings, not the volumes. If someone hands you U-40 and you read it as U-100 you will be 2.5 times out, and that error has a direction — it is always an overdose.

BenResearch_OR said:

Peptide reconstitution guide — BAC water volumes and concentrations Posting this as an important update for the other peptides & research compounds…

I am going to disagree with reconstituting low as a general rule. More diluent, more punctures, more in-use days at room temperature, and the stability trade-off is real. Precision is not the only variable being optimised.

Taking the question as asked, rather than the general version of it. Concentration choice is a precision decision, not a preference. Reconstitute high and every dose is a tiny volume where one unit of syringe error is a large fraction of the dose. Reconstitute low and you get more graduations per dose, so the same hand tremor costs proportionally less. Against that, more diluent means more benzyl alcohol and a shorter comfortable in-use window.

Dr.ObesityLA said:

The arithmetic is right and one caveat matters: a U-40 syringe changes the markings, not the volumes.

Same position here, arrived at the long way round. Dead space is the answer to the missing dose. A fixed-needle insulin syringe holds a few microlitres in the hub and needle after the plunger bottoms out, and on small draws that is a measurable percentage of every dose. Across ten draws it adds up to most of an eleventh, which is exactly the "nine draws from a ten-dose vial" complaint. Luer-lock syringes are worse; low-dead-space fixed-needle designs are better.