Posting this under the heading it deserves: A calculator that gives a right answer to the wrong question Everything below is what sits behind that.
Posting the calculation with the inputs, so that somebody can disagree with a step rather than with the answer.
Inputs: 15 mg in 3 mL, target 0.25 mg, U-100 barrel. Working shown below in the order I did it.
I have checked it twice by the same route, which is not the same as checking it twice.
The opening post describes the usual case. This is about the unusual one.
Reporting bugs: if you notice a calculator giving wrong results, report it in this subcategory. Bugs are fixed when identified.
Adding the caveat now so it does not have to be extracted later.
The opening post is the version of this I will quote in future. One addition.
Agreed on calculator, with one qualification that I think matters. The reasoning holds for the case as described. Change the starting assumption and it does not, and the starting assumption is the part nobody states.
Useful. I have added it to my own notes with the date on it.
The arithmetic in post #3 is right; the assumption feeding it is the part to check.
Marking my uncertainty on calculator explicitly. I am confident about the direction, much less confident about the size, and not confident at all that it generalises past the case in the first post.
Answering the question post #2 raises rather than the one it answers.
Nothing a calculator produces is medical advice, and a correct calculation on inappropriate inputs is still an inappropriate answer.
Not the whole picture, but the part of it I can speak to.
Why calculators are not medical advice: they do arithmetic. Medical decisions are not arithmetic. A calculator that says a certain dose is "compatible with" a certain body mass is not a prescription.
Noting that I have skin in this question and have tried to discount for it.
Narrowing post #8, because the general version has more than one answer.
Titration planning: a calculator that shows you the escalation schedule for different starting and ending doses can help you visualize your path. Actual path might be slower or adjusted for tolerability.
Written in the hope of being told what I have missed.
Calculator is well covered in the tag pages, and the older discussions are better than the recent ones because they were argued out properly. Worth twenty minutes before adding to this one.
Coming back to post #9, because the follow-up matters more than the original answer.
Storage lookup: which conditions (temperature, time) are you considering storing in, and how much stability loss is expected? The calculator gives a rough estimate based on typical stability data. Not a substitute for your compound's specific stability data.
The claim is narrower than it sounds, and deliberately so.
This follows post #13 rather than contradicting it.
Do the arithmetic by hand the first few times, whatever tool you use afterwards. A calculator with a wrong input gives a confident wrong answer and there is nothing in the interface to tell you.
I would call that likely rather than established.
On post #13 — agreed on the reasoning, with one qualification.
Dose equivalence calculator: compounds have different potencies. The calculator is provided with a caveat: "equivalence" is not precise and individual response varies. It is a rough starting point, not a dose prescription.
For what it is worth, the same held on the two occasions I checked.
Picking up post #17: that is the part I would want checked first.
Dead volume is the input most calculators do not have, which is why their answer and the delivered dose differ slightly for detachable-needle configurations.
Adding it because I spent an afternoon working it out and nobody should have to twice.
Seconded. It reads as careful rather than confident, which is the right register.
A tool that refuses to give an answer when the result falls below one graduation is doing something useful. Most just print the number.
Where a calculator and your own arithmetic disagree, the productive move is to find which step differs rather than to decide which is right.
Not a strong opinion, just a consistent one.
Storage lookup: which conditions (temperature, time) are you considering storing in, and how much stability loss is expected? The calculator gives a rough estimate based on typical stability data. Not a substitute for your compound's specific stability data.
That is the shape of it. The detail is where I would expect to be corrected.
Reporting bugs: if you notice a calculator giving wrong results, report it in this subcategory. Bugs are fixed when identified.
Correct me on the arithmetic if it is wrong; I would rather know.
A saved calculation is worth more than a remembered one. Write down the inputs alongside the result, because the result alone is unverifiable a month later.
If anyone can point at the primary source I would be grateful.
On post #24 — agreed on the reasoning, with one qualification.
Dead volume is the input most calculators do not have, which is why their answer and the delivered dose differ slightly for detachable-needle configurations.
None of the above is medical advice and I am not qualified to give any.
The residual-volume question belongs in the tool rather than in a footnote, because it is the difference between the calculation and reality.
That holds for the case as described. Change the assumptions and it may not.
Dose equivalence calculator: compounds have different potencies. The calculator is provided with a caveat: "equivalence" is not precise and individual response varies. It is a rough starting point, not a dose prescription.
That is the version I use. It may not be the version that is correct.