cloudy after reconstitution — discard, right? right.
cloudy after reconstitution — discard, right? right. Not a hot take, just something I have not seen said plainly here.
Adding more water does not change how much peptide is in the vial. It changes the concentration, which changes the volume you draw for the same amount. That is the entire relationship.
Why "more water" keeps confusing people, including me for a month.
The vial contains a fixed amount of peptide. Water changes nothing about that amount. What it changes is concentration, and concentration is the divisor between the dose you want and the volume you draw.
So doubling the water halves the concentration and doubles the units for the same dose. Nothing is diluted in any sense that matters; you are simply reading a bigger number off the same barrel. Pick the water volume that puts your usual dose on a whole number of units and life gets easier.
The failure modes I have actually seen posted here, in order of frequency.
One: reconstituting at a different volume than intended and not writing it down, so the next draw is based on a remembered concentration. Two: treating units as a dose rather than a volume, which breaks the moment the concentration changes. Three: assuming a syringe is U-100 when it is not.
All three are solved by the same two habits — do the arithmetic before the water goes in, and write the result on the glass. Neither costs anything and between them they cover almost every question this board gets.
Please do not ask me what dose you should be on. I genuinely do not know and neither does anyone else here.
best — the order this archive was captured in
Research-use-only material is not approved for human use, so treat everything in this thread as arithmetic about solutions rather than instructions for a person.
Bacteriostatic water contains benzyl alcohol as a preservative, which is what makes repeated entry into the same vial reasonable. Plain sterile water has no preservative.
the number you write down is the number you will trust at 6am
The dead space question sent me down a rabbit hole for a week. It is a fraction of a unit and it is the same every draw.
Agreed — units are volume. Once that lands, the rest of the arithmetic is one division.
more water is not more drug, it is the same drug in a bigger volume
20mg into 2mL is 10mg/mL, and 1mg of that is 10 units
do the arithmetic before you reconstitute, not while holding a syringe
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
Is that a U-100 syringe? The barrel markings change the answer completely.
the powder cake sits at the bottom, the volume you add is the volume that counts
If your calculation produces a fraction of a unit, the concentration is wrong for your dose. Change the water volume until the numbers land on whole units.
Bacteriostatic or plain sterile water?
label the vial with the date as well as the concentration
Asked SGN what volume they reconstitute to for their own stability testing and they answered in one line. Useful thing to know.
twice as much water halves the concentration and doubles the units for the same dose
The lyophilised cake displaces a small volume, so the true concentration is very slightly lower than the arithmetic suggests. It is a fraction of a percent and it is dwarfed by fill tolerance.
bacteriostatic water has the preservative, sterile water does not
if the maths gives you a fraction of a unit, change the concentration
dead space in the needle hub is real and it is small
Show the arithmetic — where did the unit figure come from?
Same. I got this wrong once, caught it because the units looked absurd, and have written on every vial since.
Corrected the concentration in the title, which contradicted the body. Nothing else touched.
Small fix — a U-100 syringe is 100 units per mL. If yours is marked differently it is not U-100 and the whole calculation changes.
The arithmetic in full: concentration is mass over volume, so 20mg into 2mL gives 10mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 1mg is 1 divided by 10 millilitres, which is 10 units.
reconstituting at a round concentration makes every later dose easy
Not quite. Bacteriostatic and sterile water are not interchangeable for a multi-draw vial, and the difference is the preservative.
- 1the number you write down is the number you will trust at 6am10 comments in this branch · started by u/dexa_twice_yearly
- 2If your calculation produces a fraction of a unit, the concentration is…10 comments in this branch · started by u/cardio_endpoint_c