Microgram (mcg)

Also known as “µg”

Last updated August 2026

A unit of mass equal to one-millionth of a gram. 1 milligram (mg) = 1,000 micrograms (mcg). Many peptide doses are given in mcg while vials are labelled in mg.

The microgram-to-milligram gap is where dosing errors most often creep in, since a vial is labelled in milligrams while a dose may be specified in micrograms. Converting both to the same unit before anything else keeps the arithmetic honest: a 5 mg vial holds 5,000 mcg, so a 250 mcg dose represents one-twentieth of its contents regardless of how much water was used to reconstitute it.

Educational reference only — not medical advice. Always follow the guidance of a qualified healthcare professional.