Let’s review: mg = milligram and mcg = microgram

Worth More than Diamonds

I must say, e-Alert readers are really on the ball.

In the e-Alert “Worth More than Diamonds” (2/14/06), I responded to an HSI member’s question about why labels for medications and supplements use the abbreviation “mcg” for microgram, when the actual metric abbreviation is “ug.”

Given that “mg” is the correct abbreviation for milligram, I expect “mcg” for microgram simply looks more logical to those of us in the U.S. who didn’t grow up using the metric system. But exactly who decided to begin using “mcg” and when they did it and exactly why remains a mystery.

Less mysterious is a typo that appeared in that e-Alert. It was small, but it was caught by several members who wrote to make sure I was zigging when I intended to zag.

An HSI member named Jim sent along one of the nicer queries. He writes: “When you said: At some point, the drug and supplement industries began using ‘mcg’ to indicate ‘milligram,’ did you mean: using ‘mcg’ to indicate ‘microgram’?”

Absolutely right, Jim.

So let’s review: mg = milligram, and mcg = microgram. And until the entire world goes metric or the U.S. converts to accurate abbreviations, that’s that.