Handling and measurement
mcg vs mg
Last updated
Two units of mass that differ by a factor of a thousand. One milligram, mg, is one thousand micrograms, mcg. So 0.5 mg is 500 mcg, and 250 mcg is 0.25 mg. Labels in this space use both, sometimes on the same packet, and the two abbreviations differ by a single letter.
Why it matters here
A number written in one unit and read as the other is wrong by a thousandfold, which is the largest and easiest error available anywhere in the handling chain. A figure quoted without its unit is not a figure at all, and this is the one conversion worth doing on paper rather than in your head.
What it is not
The proper symbol for microgram is µg with a Greek mu. Mcg exists only because a keyboard cannot easily type mu and a handwritten mu was being misread as an m, and people also type ug as a substitute. All three, µg, mcg and ug, are the same unit, and none of them is mg.
Also called
- mcg
- mg
- ug
- µg
- microgram
- micrograms
- milligram
- milligrams
- mcg vs mg
- gamma
Gamma is an obsolete name for the microgram that still turns up in older literature and in some translated sources. Mcg is a deliberate anti-ambiguity spelling adopted precisely because handwritten µg was being read as mg, so the awkward form exists because of the very mistake it prevents.
Compounds carrying this term
None on file yet. This term is in the controlled vocabulary but no compound record currently uses it — which is a statement about our coverage, not about the term.