Vial into a strength
The step before the main conversion, for anyone who mixed the vial rather than reading a strength off it. The answer is a ceiling unless you measured the finished volume.
Educational arithmetic only. Not medical advice and not a dosing protocol.
Before you act on that number
This is educational arithmetic on figures entered by the reader. It is not medical advice, not a dosing protocol, and not a recommendation that anything be prepared, obtained or administered.
Nothing here states what quantity is appropriate for anyone, and there is no function in it that produces an amount to administer. A question about anyone’s health belongs with a licensed clinician who can examine the person asking.
Compounds of the kind this arithmetic is used on are largely research chemicals that are not approved by the FDA for human use. An exact calculation is not an accurate measurement: what is actually in a syringe depends on the preparation and the device, neither of which this page can see.
No qualified clinical reviewer is recorded against this site, and no credential is claimed anywhere on it. what this is not, at full length.
See the arithmetic
- Strength is the mass divided by the volume of the FINISHED solution:
strength = mass ÷ finished volume. - The finished solution is the diluent plus the room the dissolved solid takes up. With that displacement unmeasured, the finished volume is at least the diluent, so dividing by the diluent gives the highest the strength can be.
- So the answer says at most until a finished volume is entered, and any volume derived from it says at least.
- Five milligrams in 2 mL is at most 2.5 mg/mL, which is 2,500 mcg/mL, which is 250 mcg in each tenth of a millilitre.
The field nobody else offers
Mix the vial, then read the finished volume off the barrel and type it in. The strength stops being a bound and becomes a division of two measured quantities, and the label on the answer changes to match, because the uncertainty it was flagging has gone.
Whether that is worth doing depends on the mass. For one or two milligrams the displaced volume is a fraction of a percent of a 2 mL diluent volume, well inside the error of reading a 1 mL barrel. For thirty milligrams it is larger. Either way the direction is fixed: the ceiling always errs towards a stronger solution than you have, and therefore towards a shorter draw than you need.
Why this is a separate page rather than a mode on the home page
Because the two situations have different unknowns, and merging them hides that. A reader with a labelled solution has a strength and does not know the volume. A reader with a vial and a syringe of water has neither, and acquires a strength that is uncertain in a specific, nameable direction.
One form covering both would have to either drop the ceiling language, which loses the only honest thing about the second case, or carry it everywhere, which would be wrong about the first. Two pages, two sets of labels, and the main calculator takes the strength as a given because on that page it is one.