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So I stumbled on a research paper by Okuda and Takedatsu [1] that uses mμg as a symbol for the mass unit.

I couldn't find anything about this measure unit anywhere except a recommendation not to use it. So how much is 1 mμg? I suppose it means milli-micro-grams, so it should be 1 μg/1000, but it's just a guess.

Reference

Okuda, K.; Takedatsu, H. Absorption of Vitamin B12 in a Rectal Suppository. Experimental Biology and Medicine 1966, 123 (2), 504–506. DOI: 10.3181/00379727-123-31527.

andselisk
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Andyba
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    It looks like the authors wanted to use a consistent unit, rather than say the doses were 10 nanograms and 2 milligrams, they went for micrograms for both. – Sam Pering Jan 26 '21 at 11:18
  • Is there any chance this is subtle humour? The unit could be read as "mug" when stating it as nanograms, or μmg (micro-milli-grams) removes that possible confusion. – Criggie Jan 27 '21 at 09:11
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    This could happen in new publications as well when you use your graphing software incorrectly. You tell the software to graph some value, specify the unit as µg, and when the software gets an input value < 1.0, it might multiply by 1000 and prepend a m to the unit, thus converting 0.67 µg to 670 mµg. – Guntram Blohm Jan 27 '21 at 09:50
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    Less than a mug. – Comic Sans Seraphim Jan 27 '21 at 13:52

1 Answers1

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Looks like in 1966 there were still residues of double prefix notation in use.

Here's an entry from Russ Rowlett's compilation of units on ibiblio.org (Rowlett):

millimicro- (mμ-)
an obsolete metric prefix denoting 10-9 or one billionth. This prefix has been replaced by nano- (n-).

Here's what is noted on wikipedia:

Double prefixes
Double prefixes have been used in the past, such as micromillimetres or millimicrons (now nanometres), micromicrofarads (μμF; now picofarads, pF), kilomegatons (now gigatons), hectokilometres (now 100 kilometres) and the derived adjective hectokilometric (typically used for qualifying the fuel consumption measures). These are not compatible with the SI.

Reference
Rowlett, Russ. "millimicro-". How Many? A Dictionary of Units of Measurement. University of North Carolina at Chapel Hill. http://www.ibiblio.org/units/dictM.html

z1273
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    I just wonder, why it was used mcg instead of self-offering mmg for $\mu$g ? – Poutnik Jan 26 '21 at 13:14
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    @Poutnik Not sure about mmg. I also noticed that unlike the Roman numeral system that make use of both addition and subtraction of values, the historical use of double prefixes appears to go in one direction only, either to greater mounts or to smaller amounts. These are my two megamicro-cents – z1273 Jan 26 '21 at 13:24
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    @Poutnik : Once we're in the land of double prefixes, 1 mcg would be 1 milicentigram, equivalent to 10 micrograms. There is a not-universal standard use of "mcg" in parts of the healthcare industry, putatively to minimize misdosing due to handwritten conflation of cursive "m" and mu. Regarding "mmg", the micro- prefix was in widespread use prior to the SI, with published usage back to the 1870s. – Eric Towers Jan 26 '21 at 21:02
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    @Poutnik From Wikipedia: Microgram: "the recommended symbol in the United States and United Kingdom when communicating medical information is mcg." Perhaps "mc" is closer to "micro", which only has one letter "m". – Andrew Morton Jan 27 '21 at 12:32
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    This should be subtitled "Fun Ways To Abuse Units". I particularly like "hectokilometers". Maybe I'll use this to guilt my daughter when driving her back to college at the end of the week. "Do you have any idea of how far we have to take you? My heavens - it's almost FIVE HECTOKILOMETERS!!!". Fortunately, after 19 years she's used to me... :-) – Bob Jarvis - Слава Україні Jan 27 '21 at 12:53
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    @AndrewMorton Your point is well taken. The FDA noted as well that mcg is intended as microgram. I learned mcg to stand for millicentigram. Given the discussion here, I'm not so sure anymore. – z1273 Jan 27 '21 at 12:54
  • @BobJarvis-ReinstateMonica: Wow. Forth and back, it's a megameter, a.k.a a femtozettameter, or just $\mathrm{fZm}$. – Eric Duminil Jan 27 '21 at 21:03
  • @Poutnik I always thought the reason the abbreviation stuck is that "mcg" corresponds directly to the way it's pronounced, which strongly reinforces the connection. Amusingly, I just checked my Mac's dictionary, and "mcg" is given prominently as the abbreviation, with $\mu g$ in much smaller type below. – theorist May 27 '21 at 20:23