How many milligrams are in 1 milliliters of liquid morphine?

Answer 1

A millilitre (mL) is a unit of volume. A milligram (mg) is a unit of mass.

"20 mL" of morphine would imply that the morphine is suspended in a liquid, and depending on morphine's solubility in this liquid and so forth, there can be a different amount of morphine per mL. Usually a liquid suspension like this will be "X mg per mL" or "X mg/mL" as labelled on an ampoule or something similar.
For example, you one may find an ampoule that contains 4 mg/mL of morphine (in which case the answer would be 80 mg) or one that contains 20 mg/mL (in which case the answer would be 400 mg), etc.

There is no fixed answer, *but* you should know that a morphine dose is measured in mg and not mL, so if all you know is the amount of mL, it's not safe to measure out a dose.

Answer 2

This is not a valid conversion; milligrams (mg) and grams (g) are measures of weight or mass and mL (milliliters) is a measure of volume.