⚠ Contaminated BAC water from Amazon seller — endotoxin positive

kate.chem said:

I reconstituted a 10mg vial with 2ml of bacteriostatic water and I want someone to check my unit arithmetic before I draw anything, because I keep…

For anyone reconstituting dosing arithmetic peptides: the water-to-powder ratio determines your concentration. Here's my reference:

More water = easier to measure small doses but vial runs out faster. Find the balance that works for your dose.

One thing that is still open after Dr.EndoIndy’s answer:

How much material I am losing to dead space, and whether that explains why a 10mg vial gives me nine usable draws rather than ten?

quinn_sf said:

For anyone reconstituting dosing arithmetic peptides: the water-to-powder ratio determines your concentration.

Regarding dosing arithmetic multi-dose vial contamination prevention: after reconstituting, I wipe the vial stopper with a fresh alcohol swab before EVERY single draw. I also never touch the stopper with my fingers and use a new needle for each draw.

Even with bacteriostatic water preservative, contamination is cumulative. One sloppy draw can introduce bacteria that multiply over days. Aseptic technique isn't optional — it's essential for injectable medications.

Closing the loop on my own question.

Resolved. I wrote mg, ml and mg/ml on the vial in marker and did the division in that order, and the two of us now get the same number every time.

Dr.GutHealth said:

Regarding dosing arithmetic multi-dose vial contamination prevention: after reconstituting, I wipe the vial stopper with a fresh alcohol swab before…

Agreeing with Dr.GutHealth, 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.

If somebody has the primary source to hand I would rather cite it than paraphrase it.