# Microgram

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> Source: https://en.wikipedia.org/wiki/Microgram
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{{short description|Unit of mass}}
{{hatnote|"μg" and "ΜG" (Greek letter mu with G) redirect here. For microgravity, see [micro-g environment](/source/micro-g_environment). Not to be confused with [MG](/source/MG_(disambiguation)) (in Latin letters) or [uG](/source/uG_(disambiguation)) (in Latin letters).}}
{{infobox unit
| name         = microgram
| image        = Radiance multivitamins nutritional information crop.jpg
| caption      = A [nutrition facts label](/source/nutrition_facts_label) displaying, for example, the amount of [folic acid](/source/folic_acid) in micrograms
| standard     = [SI](/source/International_System_of_Units)
| quantity     = [mass](/source/mass)
| symbol       = μg
}}
In the [metric system](/source/metric_system), a '''microgram''' or '''microgramme''' is a [unit](/source/Physical_unit) of [mass](/source/mass) equal to one millionth ({{val|e=-6}}) of a [gram](/source/gram). Two different abbreviations are commonly used. The [International System of Units](/source/International_System_of_Units) (SI) uses '''μg''', where the [SI prefix](/source/Metric_prefix) "[micro-](/source/micro-)" is represented by the Greek letter [μ](/source/Mu_(letter)) (mu). The abbreviation '''mcg''' is preferred for medical information in the United States (US), but prescription writing guidance in the United Kingdom advises that "microgram" should not be abbreviated.<ref>{{cite web |title=Prescription writing |url=https://bnf.nice.org.uk/medicines-guidance/prescription-writing/ |website=BNF |publisher=National Institute for Health and Care Excellence |access-date=9 November 2025}}</ref> A third abbreviation, the Greek letter '''[γ](/source/%CE%B3)''' (gamma), is no longer recommended.<ref>[https://www.nist.gov/pml/weights-and-measures/publications/nist-handbooks/handbook-133 NIST Handbook 133 – 2018] {{Webarchive|url=https://web.archive.org/web/20180804140757/https://www.nist.gov/pml/weights-and-measures/publications/nist-handbooks/handbook-133 |date=2018-08-04 }}, [https://www.nist.gov/sites/default/files/documents/2017/04/28/12-apde-gentab-11-hb133-final.pdf#page=17 Appendix E. General Tables of Units of Measurement, page 159 (17)] {{Webarchive|url=https://web.archive.org/web/20170505220914/https://www.nist.gov/sites/default/files/documents/2017/04/28/12-apde-gentab-11-hb133-final.pdf#page=17 |date=2017-05-05 }}</ref>
The US [Institute for Safe Medication Practices](/source/Institute_for_Safe_Medication_Practices) (ISMP) and the US [Food and Drug Administration](/source/Food_and_Drug_Administration) (FDA) recommend that mcg should be used, rather than μg, when communicating medical information.<ref>{{cite web |title=ISMP's List of Error-Prone Abbreviations, Symbols, and Dose Designations |url=https://www.ismp.org/recommendations/error-prone-abbreviations-list |access-date=2018-03-28 |publisher=ISMP |archive-date=2018-01-27 |archive-url=https://web.archive.org/web/20180127224608/http://www.ismp.org/tools/errorproneabbreviations.pdf |url-status=live }}</ref> This is due to the risk that μ might be misread as [m](/source/milli-), for "milli-", which is equal to one thousandth ({{val|e=-3}}). Such a misreading could result in a thousandfold [overdose](/source/Drug_overdose) of a drug or medicine. However, mcg is also the symbol for the obsolete unit millicentigram, derived from the [centimetre–gram–second system of units](/source/CGS) and equal to 10&nbsp;μg.

== Typography ==
Usually, a sequence of the [Unicode](/source/Unicode) code point {{unichar|03BC|}} followed by the Latin letter {{unichar|0067|}} should be used. However, if μ is not available it [may be represented](/source/Micro-) with {{unichar|0075}} or the legacy Unicode symbol {{unichar|00B5|Square Mu G}}. In [Chinese, Japanese and Korean](/source/CJK_characters) writing a [fullwidth](/source/fullwidth) version {{unichar|338D|Square Mu G}} should be used.<ref name="Unicode-U3300">{{cite web |url=https://www.unicode.org/charts/PDF/U3300.pdf |access-date=May 24, 2019 |title=The Unicode Standard 12.0 – CJK Compatibility ❰ Range: 3300—33FF ❱ |author=Unicode Consortium |author-link=Unicode Consortium |date=2019 |website=Unicode.org |archive-date=September 30, 2023 |archive-url=https://web.archive.org/web/20230930221351/http://www.unicode.org/charts/PDF/U3300.pdf |url-status=live }}</ref>

== See also ==
{{wiktionary|microgram|μg|mcg}}
* [List of SI prefixes](/source/Metric_prefix)
* [Orders of magnitude (mass)](/source/Orders_of_magnitude_(mass)), listing a few items that have a mass of around 1&nbsp;μg.

== References ==
{{reflist}}

Category:SI derived units
Category:Units of mass

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Adapted from the Wikipedia article [Microgram](https://en.wikipedia.org/wiki/Microgram) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Microgram?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.