three years of concentration threads, summarised so you do not have to read them
three years of concentration threads, summarised so you do not have to read them — a position I have arrived at slowly and would like tested.
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.
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.
The arithmetic in full: concentration is mass over volume, so 5mg into 1mL gives 5mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 2.5mg is 2.5 divided by 5 millilitres, which is 50 units.
Sceptical readings welcome. The confident ones are the ones I distrust.
best — the order this archive was captured in
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.
If your calculation produces a fraction of a unit, the concentration is wrong for your dose.
Right, and the arithmetic behind it: 15mg in 3mL is 5mg/mL, so 0.5mg is 10 units.
15mg into 3mL is 5mg/mL, and 1mg of that is 20 units
Correction: that gives 10 units, not what you have written. 20mg into 1mL is 20mg/mL and the division follows from there.
Are you accounting for the powder volume, or is that where the confusion is?
units are a volume on a U-100 syringe, not a dose
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.
Show the arithmetic — where did the unit figure come from?
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.
Aim the stream down the wall of the vial rather than into the cake. Reconstitution is a solubility problem, not a mixing problem, and mechanical shear does nothing helpful.
label the vial with the date as well as the concentration
Spent 6 weeks confused about this until somebody drew the table for me. 10mg, 2mL, 5mg/mL, 2mg is 40 units. That is the whole thing.
That only works if the fill weight is exactly the label weight, and it usually is not exactly anything.
Cosigning the round-number approach. Reconstituting to something awkward is how you end up drawing 27.5 units at six in the morning.
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