Why mg cannot convert directly to mL
Milligrams measure mass, while millilitres measure liquid volume. A direct conversion requires the concentration in mg/mL.
mL = required mg ÷ concentration in mg/mL
Mathematical example:
At a concentration of 5 mg/mL, a labelled amount of 1 mg occupies 0.2 mL.
Where concentration comes from
For a prepared vial, concentration is calculated by dividing the total labelled milligrams by the final liquid volume. Always use the verified final volume rather than estimating from vial size.