Blog
Mcg vs Mg on Supplement Labels: How to Convert and Check
One milligram (mg) equals 1,000 micrograms (mcg), so mixing up the two changes an amount by a factor of 1,000. The Reviralis Complete label uses both: zinc is 10 mg, which is 10,000 mcg, while selenium is 50 mcg, which is 0.05 mg. Convert to one unit before you compare any two lines.
Written by the Reviralis label deskUpdated · 4 min read
The rule01
What is the difference between mcg and mg?
A milligram (mg) is one thousandth of a gram. A microgram (mcg) is one thousandth of a milligram. So 1 mg = 1,000 mcg, and 1 mcg = 0.001 mg.
Q: Which way do I move the decimal? A: Going from mg to mcg, multiply by 1,000, which moves the point three places right. Going from mcg to mg, divide by 1,000, which moves it three places left.
The symbol for micro is the Greek letter mu, written as the letters "mcg" on labels so that it is not mistaken for "mg".
On the panel02
Which lines on the Reviralis label use mcg and which use mg?
The panel mixes both units, usually with the larger amounts in mg and the smaller in mcg. The table converts several lines into the other unit.
| Line | Printed | In mcg | In mg |
|---|---|---|---|
| Zinc | 10 mg | 10,000 | 10 |
| Vitamin B6 | 12 mg | 12,000 | 12 |
| Selenium | 50 mcg | 50 | 0.05 |
| Chromium | 12 mcg | 12 | 0.012 |
| Manganese | 0.4 mg | 400 | 0.4 |
| Copper | 0.052 mg | 52 | 0.052 |
| Biotin | 3 mcg | 3 | 0.003 |
Copper and manganese are printed in mg with decimals, while selenium and chromium are in mcg. The mix is normal, and it is where slips happen.
The slip03
What happens if I swap mcg and mg?
Swapping them changes the amount by 1,000 times, which turns a harmless line into a big mistake or hides a real one.
Suppose you read the B6 line, 12 mg, as 12 mcg. You would think it was 1,000 times smaller than it is. Now read the selenium line, 50 mcg, as 50 mg. You would think it was 1,000 times bigger. The adult upper limit for selenium is 400 mcg (NASEM 2019, DRI Tolerable Upper Intake Levels for Elements), so 50 mg would be 125 times over, and the real 50 mcg is 12.5%.
The same slip matters most for biotin. High-dose biotin can interfere with some lab tests (NIH ODS, Biotin), and the Reviralis line is 3 mcg, a tiny amount. A misread line of 5 mg would be more than 1,600 times larger.
Reviralis: from $49 a bottle60 capsules a bottle · 2, 3 or 6 bottles · free US shipping on 3 and 6 · 60-day money-back guarantee
See packsDouble-check04
How do I double-check a unit before I compare labels?
Convert both lines to the same unit first, then compare. Three habits catch almost every slip.
Put both amounts in mcg
Mcg avoids decimals for small lines. 0.052 mg becomes 52 mcg.
Check the limit's unit
A limit may be in mg while the label is in mcg. Convert the limit, not just the label.
Sanity-check against the percent
If the amount and the percent Daily Value disagree by 1,000, a unit is wrong. See what percent Daily Value means.
The same rule applies to the 661 mg blend. It is milligrams, so the whole blend is 0.661 g, and the last name is at most 36.8 mg. See the Reviralis blend.
Before you buy05
Does the unit change what Reviralis can do?
No. A unit tells you how much of a nutrient the label prints, not what it does. Reviralis is a supplement, not an antiviral.
Herpes has no cure, and prescription antivirals are the proven care (CDC, About Genital Herpes). No source we found shows that Reviralis prevents or reduces outbreaks. If you take a prescribed antiviral, keep taking it as directed and ask a clinician about any new supplement.
FAQ06
Reviralis questions people ask
How many mcg are in one mg?
One mg holds 1,000 mcg. To convert mg to mcg, multiply by 1,000; to convert mcg to mg, divide by 1,000. For example, 0.4 mg of manganese is 400 mcg, and 50 mcg of selenium is 0.05 mg.
Is mcg the same as ug?
Yes, the symbol for microgram is mcg or the Greek mu with g, and ug is a typing shortcut for the same unit. Supplement labels print mcg so that it cannot be misread as mg. All three mean one millionth of a gram.
Why do some labels use IU instead of mcg?
IU, or international unit, is an older unit that measures activity, not weight, so its conversion differs for each nutrient. Newer US labels use mg or mcg. Do not convert an IU figure without the factor for that nutrient and form.
Which unit is bigger, mg or mcg?
The milligram is bigger. One mg equals 1,000 mcg, so 1 mg is a thousand times larger than 1 mcg. A line printed as 12 mg holds far more than a line printed as 12 mcg.
Who wrote this07
Written and reviewed by
Pages built from the label, the order page and linked NIH, FDA, FTC, Mayo Clinic and peer-reviewed sources.
Last updated . Read our editorial standards and how we check reviews. This website is the information site for a USA Authorized Reviralis Retailer. It is not the manufacturer or the distributor named on the label. We earn money when you buy through our order links.
Keep reading
More about Reviralis
USA Authorized Reviralis Retailer
Ready to try Reviralis?
Read the label warning, check your medicines with your doctor or pharmacist first, then pick a pack. Six bottles cost the least per bottle; three and six ship free in the US; every pack carries the 60-day money-back guarantee.
- Secure checkout on the sales site
- 60-day money-back guarantee
- Ships from the U.S.