ingrid_STO said:

Most of what circulates confidently in this community traces back to one summary of one study, and the qualifier was dropped somewhere in the third…

Adding the part of the answer the thread has not reached. Order of operations matters more than any single choice here: establish a baseline, change one thing, wait long enough for it to express itself, then measure again under the same conditions.

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.

Following on from ingrid_STO — and this may be the naive question:

Did your prescriber agree with that reading, and if not what was their objection?

TirzTom said:

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.

I read this differently from TirzTom, on substance rather than tone. The objection nobody has made: this only works if the measurement is doing what we assume it is doing, and that assumption has not been tested here.

TirzTom said:

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.

Right, and the exception is worth naming rather than left implied, because the exception is where people get into trouble.