Knowing How Many Doses Are Left in a Vial

The question that catches people out is not how to draw a dose. It is how many
doses are still in the vial, and therefore when the next one needs to be ordered.
Getting this wrong means either a gap in the schedule or a shelf of vials that
expire before they are used.

The arithmetic is simple, the bookkeeping is not

A vial holds a known number of milligrams. Divide that by your current dose and
you have the theoretical dose count. A 10 mg vial at 1 mg per week is ten doses.
That number is correct and almost never matches reality, for three reasons.

First, dead volume. Every draw leaves a little solution in the needle hub and the
syringe tip. It is small, but across ten draws it is often most of one dose.

Second, titration. If your dose changes partway through a vial, the remaining
count changes with it. Six doses left at 1 mg becomes three doses at 2 mg, and
the moment you make that change your mental estimate is stale.

Third, discard dates. Reconstituted solution has a usable life measured in weeks,
not months. A vial with four doses left and eight days of life left has four
doses on paper and maybe one in practice.

What to actually track

Track two numbers per vial and the rest follows: milligrams drawn to date, and
the date it was reconstituted. From those you can derive remaining volume,
remaining doses at any dose level, and days until discard. Working the numbers
out each week by hand is where errors creep in, which is the argument for a
Peptide Tracker & Calculator over a spreadsheet you have to
remember to update correctly.

A reorder rule that works

Set your reorder trigger by time, not by count. When the earlier of "three doses
remaining" or "twelve days of vial life remaining" is hit, order. Time based
triggers survive dose changes; count based triggers do not.

Write the trigger date on the vial label the day you reconstitute it. If you keep
a running dose log, put it there as well, but the label is
the copy you will actually see.