In the
metric system
The metric system is a system of measurement that standardization, standardizes a set of base units and a nomenclature for describing relatively large and small quantities via decimal-based multiplicative unit prefixes. Though the rules gover ...
, a microgram or microgramme is a
unit of
mass equal to one millionth () of a
gram. The unit symbol is μg according to the
International System of Units (SI); the recommended symbol in the United States and United Kingdom when communicating medical information is mcg. In μg, the prefix symbol for
micro- is the Greek letter
μ (mu).
Abbreviation and symbol confusion
When the Greek lowercase "μ" (mu) is typographically unavailable, it is occasionally – although not properly – replaced by the Latin lowercase "u".
The United States–based
Institute for Safe Medication Practices (ISMP) and the U.S.
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
(FDA) recommend that the symbol μg should not be used when communicating medical information due to the risk that the prefix
μ (micro-) might be misread as the prefix
m (milli-), resulting in a thousandfold overdose. The ISMP recommends the non-
SI symbol mcg instead. However, the abbreviation mcg is also the symbol for an obsolete
centimetre–gram–second system of units unit of measure known as millicentigram, which is equal to 10 μg.
Gamma (symbol:
γ) is a deprecated non-SI unit of
mass equal to 1 μg.
NIST Handbook 133 - 2018Appendix E. General Tables of Units of Measurement, page 159 (17)
/ref>
A fullwidth version of the "microgram" symbol is encoded by Unicode
Unicode or ''The Unicode Standard'' or TUS is a character encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized. Version 16.0 defines 154,998 Char ...
at code point for use in CJK contexts.
See also
* List of SI prefixes
* Orders of magnitude (mass), listing a few items that have a mass of around 1 μg.
References
{{reflist
SI derived units
Units of mass