mcg

Units & Measurements abbreviation · Metric and SI Unit

mcg
Stands forMicrogram
CategoriesUnits & Measurements

mcg stands for Microgram, a metric and SI unit abbreviation also used in medicine.

One millionth of a gram, used for potent drugs, hormones and vitamins such as vitamin B12, vitamin D and folate. The SI symbol is μg, but mcg is preferred in medicine and on supplement labels because a handwritten μ can be mistaken for m.

Example: Levothyroxine 75 mcg by mouth once daily on an empty stomach.

Usage notes

The Joint Commission and ISMP recommend mcg over μg, since misreading micrograms as milligrams produces a thousandfold dosing error. US Supplement Facts panels list vitamin D in mcg, sometimes with IU alongside: 20 mcg equals 800 IU. Folate is labeled in mcg DFE (dietary folate equivalents). It is read aloud as "micrograms", not as letters.

More metric and SI unit abbreviations

  • km² – Square kilometer
  • kN – Kilonewton
  • kt – Kiloton (TNT equivalent)
  • L – Liter
  • ly – Light-year
  • m – Meter
  • mg – Milligram
  • MKS – Meter-kilogram-second system
  • mL – Milliliter
  • mm – Millimeter
  • mmol – Millimole
  • mol – Mole

See all 64 metric and SI unit abbreviations →

Edited by the AbbreviationList.com team. Spotted an error or a missing meaning? Contact us.